Preheat the oven to 350°F with the rack in the middle. Heat a large, oven-proof skillet over medium-high heat. Add the beef when the pan is hot.
Break up the meat with a spatula and cook, stirring occassionally, for 5 to 7 minutes or until it’s no longer pink.
Mix in the onion and bell pepper. Cook for 5 minutes until softened.
Stir in the riced cauliflower and the minced garlic.
Next, mix in the salsa, oregano and chili powder. Season to taste with salt and pepper.
Remove the skillet from the heat, and pour in the whisked eggs. Gently stir to incorporate, and smooth the top of the casserole with a spatula. Top with the sliced tomatoes (cut-side up) and hot pepper, if using.
Put the skillet in the oven and bake for 40 to 45 minutes or until the eggs are set and browned on the edges.
Rest the casserole for 5 minutes, and top with cilantro if desired.