Whisk together the olive oil, Dijon mustard, lemon juice, salt and pepper in a small mixing bowl. Brush or pour over the tuna steaks and let marinate for 15 minutes or so while you make the salsa. Then grill for 5-7 minutes per side depending on thickness. For the salsa, combine the chopped tomato, diced red onion, parsley, pepper flakes or tobasco, red wine vinegar, olive oil, salt and pepper in another mixing bowl. Mix well and then spoon over the grilled tuna steaks while they’re still hot.