Heat up grill to a medium heat.
Mix together soy sauce and vinegar, then pour over halibut on both sides.
Sprinkle both sides of halibut with garlic powder, and set aside.
Pour lemon over butter and heat until butter melts and stir to combine.
Brush grill with oil to prevent fish from sticking.
Generously brush one side of the halibut with lemon butter, then place on grill, lemon butter side down
Grill approx. 3 minutes then brush top side of halibut with lemon butter before, flipping over.
Check internal temperature regularly while cooking.
Remove from grill when fish reaches 135°F.
Place on a board, tent with aluminum foil and allow to rest for a minute or two.
Place lemon slices on grill and cook until golden on both sides.
Serve with preferred sides