Preheat your oven to 350ºF (175ºC).

In a large skillet, heat a drizzle of oil over medium-high heat. Add the frozen cauliflower rice and sauté for about 5–7 minutes, then transfer to a greased casserole dish.

In the same skillet, add oil if needed, and introduce the ground beef, red bell pepper, and white onion. Cook until browned and softened, about 7–10 minutes.

Drain any excess fat, stir in taco seasoning, tomato paste, and a splash of water, cooking for 2–3 minutes until combined.

Pour the beef mixture over the cauliflower rice in the casserole dish and top with shredded cheese.

Bake in the preheated oven for 10–15 minutes or until the cheese is melted and bubbly.

Let the casserole rest, then spread sour cream on top and add your favorite toppings before serving.