Place thyme, fennel seeds, olive oil, red pepper flakes and salt in a bowl and blend well. Coat tuna steaks with the mixture, pressing it into the flesh. Wrap each filet tightly in plastic wrap and refrigerate for 2 hours or up to overnight.

Preheat your grill to high and sear tuna for 3 to 4 minutes on each side or until the inside temperature is 140º F. (It will cook 5 degrees more after you remove it from the heat.) Don’t overcook the tuna. You also may do this in a heavy sauté pan over medium-high heat using a little peanut or vegetable oil.

Place tuna on a serving platter. Drizzle with olive oil and lemon juice if you like. Scatter garnish ingredients over fish and accompany the platter with the Caramelized Onion Jam.