Preheat the oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and minced garlic. Sauté until the onions are translucent, about 3-4 minutes.
Add the ground beef to the skillet. Cook until browned and no longer pink, stirring occasionally. Drain any excess fat.
Stir in the drained diced tomatoes, gluten-free beef broth, frozen mixed vegetables, gluten-free pasta, Italian seasoning, salt, and pepper. Mix everything well.
Bring the mixture to a simmer and cook for about 5 minutes, allowing the pasta to start cooking and absorb some of the liquid.
Transfer the mixture into a greased 9x13 inch casserole dish. Spread it evenly.
Sprinkle the shredded cheddar cheese on top of the casserole.
Bake in the preheated oven for 25 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes before serving.
Garnish with fresh parsley if desired, and serve warm.