Set a large deep skillet (or sauté pan) over medium heat. Place the breadcrumbs, cumin, chili powder, 1 1/2 teaspoons salt, and 1/2 teaspoon black pepper in a shallow dish. Mix by hand, then press the tilapia fillets in the breadcrumbs. Be sure to coat the fish well on all sides. Once the pan is hot, add 1 tablespoon butter, and 1 tablespoon oil.
Lay the breaded tilapia fillets in the skillet. Cook for 4-5 minutes per side, until golden brown. Press the thickest part of the tilapia fillet. If it seems dense and springs back when you press it, it's done. Remove the fish from the pan and set aside.
Use a paper towel and spatula to wipe the black crumbs out of the pan. Add the remaining butter and oil. Once melted, add the onions to the skillet.
Sauté the onions for 2 minutes, then add in the red bell peppers. Stir and sauté another 2 minutes. Pour in the black beans, corn, and chopped mango. Stir and sauté until the corn is warmed through. Then add the chopped cilantro and lime juice. Taste, then salt and pepper as needed.
Place the tilapia over the black bean mixture to keep warm. Then serve!