Oil a baking dish. Rub oil on the inside of each prepared pepper. Sprinkle with salt and pepper and roast for 15 minutes at 400°F.
Heat a skillet and add oil and saute the onion. Add in the ground beef and cook until no longer pink.
Stir in garlic and cook. Then add tomato sauce, cauliflower rice, Italian seasoning, salt and pepper. Sprinkle with red pepper flakes. Cook for 2 minutes.
Turn off heat and stir in half of the fontina cheese and all of the parmesan. Spoon this mixture into the par-baked peppers. Top each one with remaining fontina.
Lower to 350°F and bake for 20 minutes. Sprinkle with fresh basil or parsley if desired and serve warm. Enjoy!