Place the oven rack in the top portion of the oven. Preheat the broiler to high, leaving the door slightly open. The high temperature will give the outside of the fish that signature crust.
Combine the olive oil, lime juice, cornstarch, ancho chili powder, dried oregano, garlic powder, onion powder, salt and pepper in a shallow bowl that's large enough to dip the fish in.
Line a large baking sheet with foil and set aside. Dip the fish in the seasoning mixture and coat both sides of the tilapia, being sure to cover the entire fish.
Place filets on the prepared baking sheet bottom side up. Broil for 4 minutes, then carefully flip the filets over. Broil another 4 or 5 minutes, or until fish flakes easily with a fork.
Notes
Pat fish with a paper towel before dipping in seasoning mixture.
Cooking time may vary depending on the size and thickness of the fish.
Substitute lemon juice and lemon wedges for lime, if preferred.
Experiment with a different spice rub.
Bake with lemon slices.
Add cayenne pepper for extra heat.
Add a touch of brown sugar, honey, or maple syrup to the spice mixture for a touch of sweetness.