Warm the pan: Heat olive oil in a large oven-safe skillet over medium heat. Preheat your broiler if you plan to melt the cheese on top in the oven.
Sauté the aromatics: Add onion and bell pepper. Cook 3–4 minutes until softened.
Stir in mushrooms and cook another 2 minutes. Add garlic and cook 30 seconds until fragrant.
Brown the turkey: Scoot the veggies to the edges and add the ground turkey to the center. Season with a pinch of salt and pepper.
Cook, breaking it up with a spatula, until no longer pink and lightly browned, about 5–7 minutes.
Season like a pizzeria: Stir in oregano, basil, fennel seeds, and red pepper flakes. Toast the spices for 30 seconds to bloom their flavor.
Add sauce elements: Stir in tomato paste and cook 1 minute. Pour in crushed tomatoes (or pizza sauce).
Mix well, then taste and adjust salt and pepper. If using turkey pepperoni or cooked sausage, fold it in now.
Simmer and thicken: Reduce heat to medium-low. Let it bubble gently for 5–7 minutes, stirring occasionally, until slightly thickened.
You want a saucy, scoopable consistency.
Cheese it: Sprinkle mozzarella and Parmesan evenly over the top. If you’re staying on the stovetop, cover with a lid and cook 2–3 minutes until melted. For a bubbly, browned top, slide the skillet under the broiler for 1–3 minutes.
Watch closely to avoid burning.
Finish and serve: Remove from heat. Garnish with chopped fresh basil or parsley. Serve as-is for a low-carb option, or spoon over cooked pasta, zucchini noodles, spaghetti squash, or toasted garlic bread.