Preheat and prep: Heat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish and set aside.

Cook the meat: In a large skillet over medium heat, brown the Italian sausage, breaking it up as it cooks. Season with a pinch of salt and pepper. When fully cooked, drain excess fat if needed and set the meat aside.

Sauté the veggies: In the same skillet, add olive oil. Sauté onion and bell pepper for 3–4 minutes until softened. Stir in mushrooms and cook until they release moisture and begin to brown. Add garlic and cook for 30 seconds until fragrant.

Cook the base: Add the riced cauliflower (or sliced zucchini) to the skillet. Cook 5–7 minutes, stirring often, until tender and most of the moisture cooks off. Getting rid of excess water now keeps the casserole from turning soggy.

Season the mixture: Stir in Italian seasoning, crushed red pepper (if using), and a light sprinkle of salt and pepper. Taste and adjust seasoning.

Combine with sauce: Return the cooked sausage to the skillet and pour in the marinara. Stir to coat everything evenly. Simmer 1–2 minutes to meld flavors.

Add eggs and cheese: Remove the skillet from heat. Whisk the eggs in a small bowl. Stir the eggs into the warm mixture, then fold in 1 cup of mozzarella and 1/4 cup Parmesan. The eggs help bind the casserole without adding carbs.

Assemble: Spread the mixture evenly in the prepared baking dish. Top with the remaining mozzarella and Parmesan. Scatter black olives and pepperoni on top.

Bake: Bake for 18–22 minutes, until the cheese is melted and bubbling. For a golden top, broil for 1–2 minutes at the end, watching closely.

Rest and serve: Let it rest for 5–10 minutes to set. Garnish with fresh basil or parsley. Slice and serve.