Make the marinade: Juice the orange and blend it with basil, mint, and capers.
Marinate the tuna: Soak the tuna filets in the sauce for 15 minutes.
Crust the filets: Remove the tuna and press sesame seeds onto both sides.
Sear quickly: Heat the olive oil in a pan. Sear the tuna for about 45 seconds per side, spooning over any remaining marinade.
Serve hot: Plate immediately and enjoy with a crisp glass of white wine.