Season the chicken breasts with salt, black pepper, garlic powder, and cumin. Heat olive oil in a skillet and cook the chicken for 5-7 minutes on each side until golden brown. Remove and slice into strips.
In the same skillet, sauté diced onion and bell pepper for 3-4 minutes until soft. In a bowl, mix sautéed vegetables with black beans, corn, and salsa.
Grease a baking dish, layer sliced chicken, then pour the vegetable mixture over it. Mix sour cream with half of the cheddar cheese and spread over the top. Sprinkle remaining cheese on top.
Preheat oven to 375°F. Bake for 25-30 minutes until cheese is melted and bubbly. Let cool for a few minutes before serving.