Pulse 4 cloves garlic, 1 cup virgin olive oil, 1 Tbsp white wine vinegar, 2 Tbsp lemon juice, 4 stems fresh basil (strip leaves, toss stems), 1 tsp salt, 1/2 tsp pepper in food processor until combined. Pour over tuna steaks. Marinate for an hour at room temperature. Flip after an hour to coat the other side. Brush marinade on fish during cooking.To grill, cook each side for 4 minutes.