Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 3/4 cups (330 g) cake or all-purpose flour
- 2 1/2 tsp baking powder, 1/2 tsp baking soda, 1 tsp fine salt
- 1 3/4 cups granulated sugar
- 1/2 cup unsalted butter (softened) + 1/2 cup neutral oil
- 4 large eggs, 2 tsp vanilla extract
- About 1 cup fresh key lime juice total (for cake, curd, frosting)
- 2–3 Tbsp finely grated key lime zest
- 1 cup buttermilk
- 4 large egg yolks, 3/4 cup sugar, 4 Tbsp butter, 2 tsp cornstarch (for curd)
- 16 oz cream cheese + 1 cup butter + 5–6 cups powdered sugar (for frosting)
- 1 cup heavy cream + 2 Tbsp powdered sugar (for whipped cream)
- 1 cup graham cracker crumbs + 3 Tbsp melted butter + 2 Tbsp sugar
- Thin lime slices and extra zest for garnish
Do This
- 1. Make key lime curd: cook lime juice, zest, sugar, yolks, and cornstarch until thick; whisk in butter and chill completely.
- 2. Bake cake layers: mix dry ingredients, cream sugar with butter and oil, add eggs and flavorings, then alternate dry mix with buttermilk and lime juice; bake 3 x 8-inch layers at 350°F (175°C) for 20–24 minutes; cool.
- 3. Stir graham crumbs with sugar and melted butter; toast briefly in the oven until fragrant; cool.
- 4. Beat cream cheese and butter, add powdered sugar, lime juice, zest, vanilla, and a splash of cream to make frosting.
- 5. Whip cold heavy cream with powdered sugar and vanilla to soft, pipeable peaks; chill.
- 6. Assemble: layer cake with a dam of frosting and a pool of lime curd between each layer; crumb coat and chill.
- 7. Frost smoothly, press graham crumbs around the base, pipe whipped cream swirls on top, and garnish with lime slices and extra zest.
Why You’ll Love This Recipe
- All the bright, tangy flavor of classic Florida key lime pie, transformed into a show-stopping layer cake.
- Soft, tender lime-scented cake layered with silky key lime curd and lime cream cheese frosting for maximum citrus punch.
- Graham cracker crumbs, whipped cream, and fresh lime slices tie everything back to the beloved pie.
- Great make-ahead dessert: the curd and cake layers can be prepared in advance, and the flavors deepen as it chills.
Grocery List
- Produce: Key limes (or regular limes), optional small bouquet of flowers for serving table.
- Dairy: Unsalted butter, cream cheese, buttermilk, heavy cream, eggs.
- Pantry: All-purpose or cake flour, granulated sugar, powdered sugar, graham crackers, baking powder, baking soda, vanilla extract, neutral oil (canola or vegetable), fine salt, cornstarch.
Full Ingredients
For the Key Lime Cake Layers
- 2 3/4 cups (330 g) cake flour or all-purpose flour, spooned and leveled
- 2 1/2 tsp baking powder
- 1/2 tsp baking soda
- 1 tsp fine sea salt
- 1 3/4 cups (350 g) granulated sugar
- 1/2 cup (113 g) unsalted butter, softened to room temperature
- 1/2 cup (120 ml) neutral oil (canola or vegetable)
- 4 large eggs, at room temperature
- 2 tsp pure vanilla extract
- 1 Tbsp finely grated key lime zest (about 6–8 key limes)
- 1/2 cup (120 ml) fresh key lime juice, strained
- 1 cup (240 ml) buttermilk, at room temperature
- Optional: 1–2 drops green gel or liquid food coloring for a pale lime tint
For the Key Lime Curd Filling
- 1/2 cup (120 ml) fresh key lime juice, strained
- 1 Tbsp finely grated key lime zest
- 3/4 cup (150 g) granulated sugar
- 4 large egg yolks
- 2 tsp cornstarch
- Pinch of fine salt
- 4 Tbsp (56 g) unsalted butter, cut into small cubes
For the Lime Cream Cheese Frosting
- 16 oz (454 g) cream cheese, softened to cool room temperature
- 1 cup (226 g) unsalted butter, softened
- 5–6 cups (600–720 g) powdered sugar, sifted
- 2–3 Tbsp fresh key lime juice, to taste
- 2 tsp finely grated key lime zest
- 1 tsp pure vanilla extract
- Pinch of fine salt
- 1–2 Tbsp heavy cream or milk, as needed for consistency
For the Whipped Cream Topping
- 1 cup (240 ml) heavy cream, very cold
- 2 Tbsp (16 g) powdered sugar
- 1/2 tsp pure vanilla extract
For the Graham Cracker Crumb Garnish
- 1 cup (100 g) graham cracker crumbs (about 8 full sheets)
- 2 Tbsp (25 g) granulated sugar
- 3 Tbsp (42 g) unsalted butter, melted
For Decoration
- Thin slices of key lime (or regular lime), cut into half-moons or wedges
- Extra finely grated lime zest, for sprinkling
Step-by-Step Instructions
Step 1: Prepare pans and ingredients
Preheat your oven to 350°F (175°C). Grease three 8-inch (20 cm) round cake pans with butter or nonstick spray. Line the bottoms with parchment paper rounds and lightly grease the parchment as well. Dust the pans with flour, tapping out any excess.
Make sure all refrigerated ingredients for the cake (eggs, buttermilk, butter) and frosting (cream cheese, butter) are out of the fridge and coming to room temperature. Separate 4 eggs for the curd, reserving the yolks. Zest and juice a generous handful of key limes; you will need about 1 cup of juice total for the whole recipe. Strain the juice to remove seeds and pulp, then measure it out for each component.
Step 2: Cook and chill the key lime curd
In a small saucepan, whisk together the sugar, cornstarch, and salt for the curd. Add the egg yolks, lime juice, and lime zest; whisk until completely smooth and well combined. Place the saucepan over medium heat and cook, whisking constantly, until the mixture thickens and just begins to bubble, 5–8 minutes. It should coat the back of a spoon and hold a clear line when you run your finger through it.
Remove the pan from the heat and immediately whisk in the butter cubes until melted and glossy. Pour the hot curd through a fine-mesh sieve into a clean bowl to remove any bits of cooked egg or zest, pressing it through with a spatula. Press a piece of plastic wrap directly onto the surface to prevent a skin from forming. Chill in the refrigerator until completely cold and thick, at least 1 hour (or up to 3 days).
Step 3: Make the key lime cake batter
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. In a large mixing bowl (or the bowl of a stand mixer fitted with the paddle), beat the softened butter, oil, and granulated sugar on medium-high speed until very light and fluffy, 3–4 minutes. Scrape down the bowl as needed.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla and lime zest. In a measuring jug, combine the buttermilk and lime juice. With the mixer on low speed, add the dry ingredients in three additions, alternating with the buttermilk-lime mixture in two additions (dry, wet, dry, wet, dry). Mix just until the batter is smooth and no dry streaks remain. If using, beat in 1–2 drops of green food coloring for a soft pastel hue. Do not overmix.
Step 4: Bake and cool the cake layers
Divide the batter evenly among the three prepared pans (about 500–550 g batter per pan if you want to weigh it). Smooth the tops with a spatula. Bake at 350°F (175°C) for 20–24 minutes, or until the centers spring back lightly when touched and a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Let the cakes cool in their pans on a wire rack for 10–15 minutes. Then carefully run a thin knife around the edges, turn the cakes out onto the rack, peel off the parchment, and allow them to cool completely, at least 45–60 minutes. For easier assembly, you can wrap the cooled layers in plastic wrap and chill or lightly freeze them for 30–60 minutes so they are firmer and less crumbly.
Step 5: Prepare graham crumbs, frosting, and whipped cream
For the graham crumb garnish, reduce the oven temperature to 325°F (165°C). In a small bowl, stir together the graham cracker crumbs, sugar, and melted butter until the mixture resembles wet sand. Spread on a parchment-lined baking sheet and bake for 6–8 minutes, stirring once halfway, until lightly toasted and fragrant. Cool completely and gently break up any large clumps.
For the lime cream cheese frosting, beat the softened cream cheese and butter together on medium-high speed until completely smooth and fluffy, 2–3 minutes. Gradually add 5 cups of powdered sugar, mixing on low speed until incorporated, then increasing to medium-high until light and creamy. Beat in the lime juice (start with 2 Tbsp), lime zest, vanilla, and salt. If needed, add more powdered sugar to thicken, or a splash of heavy cream to loosen, until you have a smooth, spreadable frosting that holds soft peaks.
For the whipped cream topping, combine the cold heavy cream, powdered sugar, and vanilla in a chilled mixing bowl. Whip with a hand mixer or whisk until soft to medium peaks form; the cream should hold its shape but still look smooth and slightly billowy. Do not overbeat. Cover and refrigerate until ready to decorate.
Step 6: Assemble and fill the cake with lime curd
Place a small dollop of frosting in the center of your serving plate or cake board to anchor the cake. Set the first cake layer on top, bottom side down. Add about 1/2–3/4 cup of cream cheese frosting and spread it into an even layer, but leave a 1/2-inch border around the edge. Transfer some frosting to a piping bag fitted with a large round tip (or use a zip-top bag with the corner snipped) and pipe a thick ring of frosting around the outer edge of the cake layer to create a “dam.”
Gently spoon and spread about 1/3–1/2 cup of chilled key lime curd inside the frosting dam, smoothing it into an even layer. Do not overfill or it may squeeze out when you stack the layers. Top with the second cake layer, and repeat with frosting dam and curd. Place the final cake layer on top, bottom side up for the flattest surface.
Step 7: Crumb coat, chill, and decorate
Using an offset spatula, spread a thin layer of cream cheese frosting over the top and sides of the cake to seal in any crumbs. This is your crumb coat. Chill the cake for 20–30 minutes to firm up the frosting and curd layers.
Once set, apply a thicker, smooth coat of frosting over the top and sides. Use a bench scraper or straight-edged spatula to smooth the sides and top as desired. While the frosting is still slightly soft, gently press the cooled graham cracker crumbs around the bottom 1–2 inches of the cake to create a rustic “crust” effect.
Transfer the whipped cream to a piping bag fitted with a star tip (or your favorite decorative tip). Pipe swirls or rosettes around the top edge of the cake. Tuck thin lime slices into the whipped cream swirls and sprinkle with a bit of extra lime zest for a fresh, vibrant finish. Chill the cake for at least 30 minutes before slicing so the layers set and cut cleanly.
Pro Tips
- Use real key limes if possible. They are smaller and more aromatic than regular limes and give this cake its distinctive Florida key lime pie flavor. If you cannot find them, regular Persian limes still make a delicious cake.
- Strain your lime juice. Pulp and seeds can make curd and frosting grainy; straining gives a smooth, silky texture.
- Do not skip the crumb coat. A quick thin layer of frosting locks in crumbs and makes final decorating much easier and neater.
- Chill between steps. Slightly chilled cake layers, curd, and frosting are all easier to work with and help keep the filling from bulging out.
- Adjust tang to taste. If you like it extra tart, add an extra tablespoon of lime juice to the curd and a little more zest to the frosting.
Variations
- Two-layer 9-inch cake: Bake the batter in two 9-inch pans for 25–30 minutes. Increase the curd in each layer and keep the frosting and decorations the same.
- Coconut key lime cake: Fold 1 cup of lightly toasted shredded coconut into the cake batter and sprinkle extra toasted coconut over the top along with the graham crumbs.
- Simplified version: Skip the whipped cream piping and simply spread whipped cream over the top, sprinkle generously with graham crumbs and zest, and decorate with a few lime wedges.
Storage & Make-Ahead
Because of the cream cheese frosting, curd filling, and whipped cream, this cake should be stored in the refrigerator. Cover loosely with plastic wrap or keep in a cake carrier and refrigerate for up to 3 days. For the best texture and flavor, let slices sit at room temperature for 20–30 minutes before serving so the cake softens and the citrus aromas open up.
The key lime curd can be made up to 3 days in advance and kept chilled in an airtight container. Cake layers can be baked, cooled, wrapped tightly in plastic, and refrigerated for up to 2 days or frozen for up to 2 months; thaw wrapped in the fridge overnight. The cream cheese frosting can be made 1–2 days ahead and stored in the refrigerator; bring it to a cooler room temperature and re-whip briefly before decorating. Whip the cream on the day you plan to serve for the most stable, fluffy texture.
Nutrition (per serving)
Approximate values for 1 of 12 servings: about 720 calories; 42 g fat; 26 g saturated fat; 85 g carbohydrates; 1 g fiber; 63 g sugars; 8 g protein; 410 mg sodium. These numbers are estimates and will vary based on exact ingredients used and portion sizes.
