Preheat oven to 350˚ F. Prepare a baking dish by greasing it with 1 tablespoon of butter.
Place tilapia in the greased dish and season with salt and pepper.
In a small bowl, combine the breadcrumbs with 1 tablespoon of the butter, sesame seeds, and sage. Sprinkle over tilapia and bake for 6-8 minutes until just about cooked through.
Arrage the grapefruit segments on the fish and brush with remaining butter. Bake for another 2-3 minutes or until fully cooked.