¼ cup olive oil
2 Tbsp red wine vinegar
2 Tbsp chopped basil
2 tsp chopped fresh thyme
2 tsp dried tarragon
2 large garlic cloves, finely chopped
1/3 cup Mayonnaise
4 7oz tuna steaks, 1 inch thick
Whisk first 6 ingredients in shallow dish for marinade. Place mayonnaise in separate small bowl. Whisk in 1 ½ Tbsp marinade to make aioli. Set aioli aside.
Sprinkle fish with salt and pepper. Place fish in marinade dish, turning to coat evenly. Marinate at room temperature 1 hour, turning dish occasionally.
Oil grill rack. Prepare barbecue to medium high heat. Grill fish to desired doneness about 3 minutes per side for medium. Top fish with aioli and serve.