Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish.
Heat 2 tbsp olive oil in a large skillet over medium heat. Sauté onion and bell pepper 4–5 minutes until softened; add garlic and cook 30 seconds.
Add 2 lb ground beef and brown thoroughly, breaking up the meat (6–8 minutes). Drain excess fat if more than 1 tbsp remains.
Stir in spices (cumin, smoked paprika, chili powder, oregano, salt, pepper). Pour in 1 cup chicken broth and 1 cup drained diced tomatoes (if using). Simmer 2–3 minutes.
Reduce heat; add 8 oz cream cheese and ½ cup sour cream, stirring until smooth. Fold in 400 g riced cauliflower and heat 2–3 minutes until cauliflower is slightly tender. Taste and adjust seasoning.
Transfer mixture to prepared baking dish, spread evenly, and top with 2 cups shredded cheddar.
Bake 20–25 minutes until bubbly. Broil 1–3 minutes for a browned top if desired. Let rest 5 minutes.
Garnish with sliced avocado, cilantro, and green onions; serve warm.