2 tbsp soy sauce (or 2 tsp of wheat-free tamari for gluten-free option)
1 tbsp grated fresh ginger
1 clove garlic, minced
1 green onion (scallion) thinly sliced (optional)
1 tsp lemon juice
2 6-8 oz fresh, sushi-grade ahi tuna steaks (3/4-inch thick)
Mix balsamic vinegar, soy sauce, ginger, garlic, green onions and lemon juice together in a large bowl.
Place tuna steaks in bowl with the marinade, cover tightly and refrigerate for at least an hour.
Heat a non-stick skillet over medium-high to high heat. When the pan is hot, remove tuna from the marinade and sear them for 1 minute to 1½ on each side for rare tuna (keep on heat longer if you want the tuna cooked more thoroughly).
Remove from pan, and slice into 1/4-inch thick slices. Serve alone, atop a bed of lettuce or with brown rice.