Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 medium fennel bulbs (about 1.5 lb), cored and thinly sliced
- 1 medium yellow onion, thinly sliced
- 3 tbsp olive oil, divided
- 1 lb (450 g) Italian sausage, casings removed
- 3 cloves garlic, minced
- 2 tbsp tomato paste
- 1 can (28 oz / 800 g) crushed tomatoes
- 1 tsp dried oregano + 1 tsp dried basil
- 1 tsp sugar
- 1 tsp finely grated orange zest, plus more for garnish
- 8 oz (225 g) mozzarella, torn or shredded
- 1/4 cup grated Parmesan (optional)
- Salt, black pepper, red pepper flakes, fresh herbs for garnish
Do This
- 1. Preheat oven to 400°F (200°C). Lightly oil a 2-quart (2 L) baking dish.
- 2. In a large skillet, cook fennel and onion in 2 tbsp olive oil with salt and pepper over medium heat until deeply golden and caramelized, 12–15 minutes. Transfer to a bowl.
- 3. In the same skillet, brown sausage, breaking into crumbles, 6–8 minutes. Spoon off excess fat if needed.
- 4. Add garlic, red pepper flakes, and tomato paste; cook 1–2 minutes. Stir in crushed tomatoes, dried herbs, sugar, orange zest, salt, and pepper. Simmer 8–10 minutes.
- 5. Stir caramelized fennel and onion into the tomato–sausage sauce. Adjust seasoning.
- 6. Pour mixture into baking dish. Top with mozzarella and Parmesan. Drizzle with remaining 1 tbsp olive oil.
- 7. Bake 20–25 minutes until bubbling and browned. Rest 5–10 minutes, garnish with orange zest and fresh herbs, and serve.
Why You’ll Love This Recipe
- Rich, cozy flavors: sweet caramelized fennel, savory Italian sausage, and a bright tomato base with just a whisper of orange.
- Family-friendly but special enough for guests, using easy-to-find ingredients.
- Versatile main dish: serve with crusty bread, over pasta, or spooned onto creamy polenta.
- Great make-ahead potential: the sauce can be prepped in advance, then baked with cheese right before serving.
Grocery List
- Produce: Fennel bulbs (2 medium), yellow onion (1), garlic (3 cloves), 1 orange (for zest), fresh basil or parsley (for garnish)
- Dairy: Mozzarella (8 oz), Parmesan cheese (optional, about 1/4 cup grated)
- Pantry: Olive oil, Italian sausage (1 lb), tomato paste, crushed tomatoes (28 oz can), dried oregano, dried basil, red pepper flakes, sugar, kosher salt, black pepper
Full Ingredients
Roasted Fennel & Sausage Tomato Base
- 2 medium fennel bulbs (about 1.5 lb / 680 g total), fronds reserved, bulbs cored and thinly sliced
- 1 medium yellow onion, thinly sliced
- 3 tbsp olive oil, divided
- 1 tsp kosher salt, divided (plus more to taste)
- 1/2 tsp freshly ground black pepper, divided (plus more to taste)
- 1 lb (450 g) Italian sausage (mild or hot), casings removed and crumbled
- 3 cloves garlic, minced
- 1/4 tsp red pepper flakes (optional, or to taste)
- 2 tbsp tomato paste
- 1 can (28 oz / 800 g) crushed tomatoes
- 1 tsp dried oregano
- 1 tsp dried basil (or Italian seasoning)
- 1 tsp granulated sugar (to balance acidity)
- 1 tsp finely grated orange zest (from about 1/2 orange), plus extra for garnish
Cheese Topping
- 8 oz (225 g) mozzarella, torn into bite-size pieces or shredded (about 2 cups packed)
- 1/4 cup (25 g) grated Parmesan cheese (optional, for extra savory flavor)
For Serving (Optional)
- 2 tbsp chopped fresh basil or flat-leaf parsley
- Reserved fennel fronds, roughly chopped
- Crusty bread, cooked pasta, or creamy polenta
Step-by-Step Instructions
Step 1: Preheat the oven and prepare the dish
Preheat your oven to 400°F (200°C) with a rack in the center position. Lightly oil a 2-quart (2 L) baking dish or similar shallow casserole so the tomato base will not stick. Set the dish aside.
Trim the fennel bulbs by cutting off the stalks and fronds (reserve some fronds for garnish), then slice each bulb in half from top to bottom. Cut out the tough core, then thinly slice the fennel. Thinly slice the onion as well so it will caramelize evenly with the fennel.
Step 2: Caramelize the fennel and onion
Heat 2 tbsp olive oil in a large, wide skillet over medium heat. Add the sliced fennel and onion, and sprinkle with 1/2 tsp kosher salt and a pinch of black pepper. Toss to coat the vegetables evenly in oil.
Cook, stirring every couple of minutes, until the fennel and onion are deeply golden and caramelized at the edges, about 12–15 minutes. Adjust the heat if needed so they brown slowly rather than burn. A little browning on the bottom of the pan is good; it will add flavor later. When the vegetables are soft, sweet, and reduced in volume, transfer them to a bowl and set aside.
Step 3: Brown the sausage
In the same skillet (do not wipe it out), add the Italian sausage over medium to medium-high heat. Cook, breaking it into small crumbles with a spatula or wooden spoon, until well browned and cooked through, about 6–8 minutes. If the sausage releases a lot of fat, you can spoon off some, leaving about 1–2 tbsp in the pan for flavor.
Season with the remaining 1/2 tsp salt and a few grinds of black pepper. Browning the sausage well at this stage deepens the overall flavor of the dish.
Step 4: Build the tomato and orange-scented sauce
Reduce the heat to medium-low. Add the minced garlic, red pepper flakes (if using), and 2 tbsp tomato paste to the pan with the sausage. Cook, stirring constantly, for 1–2 minutes until very fragrant and the tomato paste darkens slightly in color.
Pour in the crushed tomatoes, then add the dried oregano, dried basil, sugar, and 1 tsp finely grated orange zest. Stir well to combine, scraping up any browned bits from the bottom of the skillet. Bring the mixture to a gentle simmer and cook for 8–10 minutes, stirring occasionally, until slightly thickened and saucy. Taste and adjust seasoning with more salt and pepper if needed.
Step 5: Combine sauce with caramelized fennel
Return the caramelized fennel and onion to the skillet and gently fold them into the tomato–sausage sauce until everything is evenly distributed. The fennel should be coated but still visible as tender strands throughout the sauce.
Taste again and adjust with a bit more orange zest, salt, or pepper if desired. The orange should be a subtle background note that brightens the tomato without dominating it.
Step 6: Assemble and bake
Transfer the fennel, sausage, and tomato mixture to your prepared baking dish, smoothing it into an even layer. Scatter the mozzarella evenly over the top. Sprinkle with grated Parmesan if using. Drizzle the remaining 1 tbsp olive oil over the cheese to help it brown beautifully.
Place the dish in the oven and bake at 400°F (200°C) for 20–25 minutes, or until the sauce is bubbling at the edges and the cheese is melted, golden in spots, and just beginning to brown. If you like a deeper browned top, you can switch to the broiler for the last 1–2 minutes, watching very closely to avoid burning.
Step 7: Rest, garnish, and serve
Remove the dish from the oven and let it rest for 5–10 minutes. This short resting time allows the sauce to thicken slightly so it is easier to serve.
Before bringing to the table, garnish with a sprinkle of freshly grated orange zest, chopped fresh basil or parsley, and some reserved fennel fronds for color and aroma. Serve hot, either as a hearty main dish with crusty bread, or spooned generously over pasta or creamy polenta.
Pro Tips
- Slice fennel thin for best caramelization. The thinner the slices, the more surface area you get for browning and sweetness. Aim for about 1/8–1/4 inch (3–6 mm) thick.
- Do not rush the caramelizing step. If the fennel and onion cook too quickly, they will scorch instead of sweetly browning. Adjust the heat as needed and give them time.
- Go light on the orange zest at first. Orange can quickly overpower. Start with the recommended 1 tsp in the sauce, then add a light sprinkle on top after baking so the aroma is fresh but not overwhelming.
- Control the richness. If your sausage is very fatty, drain off some of the rendered fat before adding the tomatoes so the dish does not become greasy.
- Make it saucier for pasta. If you know you will serve this over pasta, stir in 1/4–1/2 cup (60–120 ml) water or broth before baking so there is a bit more sauce to coat the noodles.
Variations
- Spicy version: Use hot Italian sausage and increase the red pepper flakes to 1/2–3/4 tsp. Add a pinch of smoked paprika for a slightly smoky note.
- Pasta bake: Stir in 8 oz (about 225 g) cooked short pasta (such as rigatoni or penne) with the fennel and sausage mixture before transferring to the baking dish. Add an extra 1/2 cup (120 ml) crushed tomatoes or a splash of pasta cooking water so it stays saucy.
- Vegetarian twist: Swap the Italian sausage for your favorite plant-based sausage or use canned lentils (drained and rinsed) plus 1 tbsp extra olive oil and an additional 1/2 tsp fennel seeds for a similar flavor profile.
Storage & Make-Ahead
Let leftovers cool to room temperature, then cover tightly and refrigerate for up to 3–4 days. Reheat individual portions in the microwave until hot, or warm the whole dish in a 350°F (175°C) oven for 15–20 minutes, covered with foil if the top is already well browned.
For longer storage, you can freeze the baked and cooled dish (well wrapped) for up to 2 months. Thaw overnight in the refrigerator before reheating in the oven. To get ahead, you can fully prepare the fennel–sausage tomato mixture up to 2 days in advance; keep it refrigerated. When ready to serve, transfer to a baking dish, top with cheese, and bake as directed, adding a few extra minutes if it is going into the oven cold.
Nutrition (per serving)
Approximate values per serving (1/4 of the recipe, without bread or pasta): about 625 calories, 32 g protein, 46 g fat, 14 g carbohydrates, 3 g fiber, and 8 g sugar. Actual values will vary based on the exact sausage and cheeses used.
