Preheat and prep: Heat your oven to 375°F (190°C).
Lightly oil a 9x13-inch baking dish.
Sauté the aromatics: In a large skillet over medium heat, warm the oil. Add onion with a pinch of salt and cook 3–4 minutes until softened. Stir in garlic for 30 seconds.
Brown the meat: Add ground beef or turkey.
Cook, breaking it up, until browned and no longer pink. Drain excess fat if needed.
Add veggies and chiles: Stir in zucchini (if using) and green chiles. Cook 2–3 minutes to soften the zucchini slightly.
Season it up: Add chili powder, cumin, smoked paprika, oregano, garlic powder, onion powder, and optional chipotle or cayenne.
Season with salt and pepper. Toast the spices 30–60 seconds.
Make the sauce: Stir in the drained fire-roasted tomatoes, tomato sauce, and broth. Simmer 4–5 minutes until slightly thickened.
Taste and adjust seasoning.
Enrich and thicken: Reduce heat to low and stir in sour cream and cream cheese until smooth and incorporated. The mixture should be saucy but not watery.
Layer the casserole: Spoon half the meat mixture into the baking dish. Sprinkle on half the shredded cheese.
Add the remaining meat mixture, then top with the remaining cheese.
Bake: Place in the oven for 15–20 minutes, until the cheese is melted and bubbly and the edges are lightly browned.
Rest and garnish: Let it rest 5–10 minutes to set. Garnish with chopped cilantro and your favorite toppings.
Serve: Scoop into bowls and enjoy as-is, or with a crisp side salad or cauliflower rice.