Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, add the olive oil and sauté the diced onion and garlic until fragrant, about 2 minutes.
Add the ground beef to the skillet and cook until browned, breaking it apart with a spoon, about 5-7 minutes. Drain excess fat if necessary.
Stir in the diced tomatoes, bell peppers, salt, pepper, and Italian seasoning. Cook for an additional 5 minutes to allow the flavors to meld.
Meanwhile, cook the gluten-free pasta according to package instructions. Drain and set aside.
In a large mixing bowl, combine the cooked pasta with the beef mixture. Stir in half of the cheddar and mozzarella cheeses.
Transfer the mixture to a greased 9x13 inch baking dish. Top with the remaining cheese and optionally sprinkle with gluten-free breadcrumbs.
Bake in the preheated oven for about 20 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for a few minutes before serving.