Prep the peppers: Heat your oven to 375°F (190°C). Slice the tops off the bell peppers and remove seeds and membranes. If they wobble, shave a thin slice off the bottoms so they stand. Brush the outsides lightly with olive oil and place them cut-side up in a baking dish.

Par-bake the peppers: Bake for 10–12 minutes to soften slightly. This helps them cook through later without turning mushy.

Sauté the aromatics: While the peppers are in the oven, heat the remaining olive oil in a large skillet over medium heat. Add the onion and a pinch of salt. Cook 3–4 minutes until translucent. Stir in the garlic and cook 30 seconds until fragrant.

Brown the meat: Add the ground beef or turkey. Break it up with a spoon and cook until browned, 6–8 minutes. Season with salt, pepper, oregano, basil, red pepper flakes, and fennel seeds if using.

Add the cauliflower rice: Stir in the riced cauliflower and cook 2–3 minutes to remove moisture. This keeps the filling from getting watery.

Build the sauce: Mix in the tomato paste and sugar-free marinara. Simmer 2–3 minutes so the flavors meld and the mixture thickens slightly.

Cheesy finishing touch: Turn off the heat. Stir in the Parmesan and 1 cup of the mozzarella. Taste and adjust salt and pepper.

Stuff and top: Spoon the filling evenly into the par-baked peppers, mounding slightly. Sprinkle the remaining 1/2 cup mozzarella over the tops.

Bake: Return the dish to the oven and bake 15–20 minutes, until the peppers are tender and the cheese is melted and lightly golden.

Finish and serve: Let rest 5 minutes. Garnish with chopped parsley or basil. Serve warm.