In a medium skillet, melt the Garlic Butter over high heat. Once the skillet is warm, add the tuna steak to the pan. Sear on both sides, about 1 minute each side.
Add lemon juice, Lemon Butter, lemon zest, salt and pepper to taste, and remove from the pan. Rest for 5 minutes.
Slice tuna steak into thin pieces and serve over mixed greens & veggies with lemon slices and olive oil.