1. Preheat grill to medium-high heat (350° to 400°).
2. Sprinkle tuna steaks with salt and pepper. Grill on greased grill racks 2 minutes on each side or until desired degree of doneness.
3. Transfer tuna to a cutting board, and cut each steak across the grain into 1/2-inch slices. Spoon Fennel-Orange Relish over tuna, and serve immediately.