Heat a large skillet over medium heat. Add the ground beef, season with salt and pepper, and cook until browned, breaking it apart as it cooks. Drain excess grease.
Add onion and garlic. Cook for 2-3 minutes until fragrant.
Stir in the chopped bell peppers and cook for 4-5 minutes until slightly softened.
Add riced cauliflower, crushed tomatoes, marinara sauce, and Italian seasoning. Stir well to combine
Cover and simmer for 6-8 minutes, until peppers are tender and cauliflower is cooked.
Sprinkle mozzarella cheese over the top, cover, and cook until melted. Serve warm and enjoy!