Rustic Blueberry Buckle with Cinnamon Streusel

Why You’ll Love This Recipe

• Plush vanilla cake that stays tender from a splash of sour cream.
• A crown of crackly cinnamon streusel that contrasts beautifully with juicy berries.
• Simple pantry ingredients, one pan, and foolproof steps.
• Great warm out of the oven, and even better with coffee the next morning.

Grocery List

• Produce: Fresh blueberries
• Dairy: Unsalted butter, whole milk, sour cream, 1 large egg + 1 large egg yolk
• Pantry: All-purpose flour, granulated sugar, light brown sugar, baking powder, cinnamon, vanilla extract, fine salt

Full Ingredients

For the Cinnamon Streusel

• All-purpose flour: 3/4 cup (90 g)
• Light brown sugar (packed): 1/2 cup (100 g)
• Ground cinnamon: 1 tsp
• Fine salt: 1/4 tsp
• Unsalted butter, melted and cooled slightly: 5 tbsp (70 g)

For the Vanilla Cake and Berries

• Fresh blueberries: 2 cups (10 oz/280 g)
• All-purpose flour: 1 3/4 cups (220 g), plus 1 tbsp (8 g) for tossing berries
• Baking powder: 2 tsp
• Fine salt: 1/2 tsp
• Unsalted butter, softened: 1/2 cup (113 g)
• Granulated sugar: 3/4 cup (150 g)
• Large egg: 1
• Large egg yolk: 1
• Vanilla extract: 2 tsp
• Whole milk: 1/2 cup (120 ml)
• Sour cream: 1/4 cup (60 ml)

Step-by-Step Instructions

Step 1: Prep the pan and preheat

Heat the oven to 350°F (175°C). Grease a 9-inch square metal baking pan and line it with a parchment sling, leaving overhang on two sides to lift the buckle out easily. Lightly grease the parchment, too.

Step 2: Make the cinnamon streusel

In a medium bowl, whisk the flour, brown sugar, cinnamon, and salt. Pour in the melted butter and stir until the mixture is evenly moistened and forms clumps. Pop the bowl into the fridge while you make the batter; a brief chill helps the streusel bake up extra craggy and crisp.

Step 3: Whisk the dry ingredients

In another bowl, whisk the flour (220 g), baking powder, and salt until well combined. Set aside.

Step 4: Cream butter, sugar, and eggs

In a large mixing bowl, beat the softened butter and granulated sugar with a hand mixer (or stand mixer) on medium speed until pale and fluffy, about 2 minutes. Scrape down the bowl. Beat in the egg, egg yolk, and vanilla until smooth and slightly thickened, about 30 seconds.

Step 5: Finish the batter

On low speed, add the dry ingredients in two additions, alternating with the milk and sour cream. Mix just until no dry streaks remain; do not overmix. In a small bowl, toss the blueberries with 1 tbsp flour to lightly coat (this helps keep them from sinking). Gently fold the berries into the batter with a spatula, taking care not to crush them.

Step 6: Assemble

Scrape the thick batter into the prepared pan and smooth the top. Using your fingers, break the chilled streusel into clumps and scatter evenly over the batter, covering from edge to edge.

Step 7: Bake and cool

Bake on the center rack for about 50 minutes, until the top is deep golden and crackly and a toothpick inserted in the center comes out with a few moist crumbs (or an instant-read thermometer registers about 200–205°F/93–96°C in the center). Cool in the pan on a rack for 10–20 minutes. Lift out using the parchment and let cool a bit more before slicing. Serve warm or at room temperature.

Pro Tips

• Use a metal pan: It conducts heat better than glass, helping the buckle rise high with a crisp streusel.
• Weigh your flour if possible (220 g for the batter) to avoid a dry cake; if using cups, fluff, spoon, and level.
• Toss berries with a little flour to reduce sinking and bleeding.
• Chill the streusel briefly; cooler clumps bake up chunkier and crunchier.
• Don’t overmix once flour goes in. Gentle mixing keeps the crumb plush and tender.

Variations

• Lemon-blueberry buckle: Add 1–2 tsp finely grated lemon zest to the sugar before creaming for a bright citrus note.
• Brown-butter streusel: Brown the 5 tbsp butter, cool to warm, then stir into the streusel for a toasty, nutty aroma.
• Mixed-berry buckle: Use a blend of blueberries and raspberries (keep total to 2 cups/280 g). Fold gently as raspberries are delicate.

Storage & Make-Ahead

Store tightly covered at room temperature for up to 2 days. For longer storage, wrap slices individually and freeze for up to 2 months; thaw at room temperature or warm in a 300°F (150°C) oven for 8–10 minutes. Streusel can be mixed up to 2 days ahead and refrigerated. The batter is best baked right after mixing, but you can measure and stage ingredients a day ahead to speed things up.

Nutrition (per serving)

Approximate for 1 of 9 servings: 440 calories, 22 g fat, 58 g carbohydrates, 5 g protein, 1 g fiber, 270 mg sodium.