Preheat the oven to 400°F. Line a baking sheet with foil and spray with non-stick cooking spray.

Put butter in a small bowl and mash it with a fork. Add olives, capers, and a pinch of garlic powder. Add salt and pepper, to taste. Stir well to blend. Form butter into discs about 1-½-inch across. Put on a plate and refrigerate until solid. (The butter can be prepared up to 2 days in advance).

Set tilapia on the baking sheet and season with garlic powder, salt, and pepper. Bake until opaque through the thickest part, about 6 to 8 minutes.

Transfer the tilapia to individual plates and top each with a disc of olive-caper butter.