Wash and dry the bell peppers. Cut in half and remove the membrane and seeds with a spoon. Place the bell peppers in a casserole dish cut side up. Season with a pinch of salt and pepper.
Heat a pan over medium-high heat. Add oil and allow to heat. Sauté onions for 3 - 4 minutes until translucent. Add garlic and cook for another minute. Add ground beef and cook for 6 - 8 minutes until beef has browned and there is no pink visible. Set aside in a bowl.
Sauté riced cauliflower in the same pan for 5-7 minutes, until softened and some moisture has evaporated.
Add marinara sauce, fresh thyme, salt, and pepper and mix together. Turn the heat down to medium-low for 2 minutes until completely heated through.
Stir in ground meat and cook until heated through. Stir in 1/2 cup of shredded cheese.
Spoon the meat and sauce mixture into the peppers. Add a sprinkle of cheese to each pepper half.
Cover with foil and bake for 30 minutes. Remove the foil and cook for a further 5 minutes.
Garnish with fresh herbs if desired, serve and enjoy.
This recipe makes 6 servings. Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. To reheat, use a microwave or heat in the oven for 15 minutes at 350 degrees until the cheese is melted and the filling has completely warmed through.