Preheat and prep: Heat the oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
Sauté the veggies: Warm the olive oil in a large skillet over medium heat.
Add the onion and bell pepper, and cook until softened, about 5 minutes. Stir in the garlic and cook 30 seconds, until fragrant.
Brown the turkey: Add the ground turkey to the skillet. Break it up with a spoon and cook until no longer pink, 5–7 minutes.
If excess liquid accumulates, let it cook off to concentrate the flavor.
Season well: Sprinkle in the chili powder, cumin, smoked paprika, oregano, red pepper flakes (if using), salt, and black pepper. Stir and cook 1 minute to toast the spices.
Add liquids and beans: Pour in the diced tomatoes with their juices and the tomato sauce. Stir in the black beans, pinto (or kidney) beans, and corn, if using.
If the mixture looks too thick, add up to 1/2 cup broth or water.
Simmer to meld flavors: Reduce heat and let the chili simmer 8–10 minutes, stirring occasionally. You want a thick, scoopable mixture. Taste and adjust salt as needed.
Assemble the bake: Transfer the chili to the prepared baking dish. Smooth the top, then sprinkle evenly with the shredded cheese.
Bake until bubbly: Place in the oven and bake 12–15 minutes, or until the cheese is fully melted and the edges are bubbling.
For a golden top, switch to broil for the last 1–2 minutes, watching closely.
Finish and serve: Let the bake rest 5 minutes to settle. Sprinkle with cilantro and green onions. Serve hot with a dollop of sour cream or Greek yogurt and a few dashes of hot sauce.