Preheat oven to 450 degrees and spray a shallow baking dish with cooking spray. Season both sides of fish lightly with salt and pepper and place in a prepared dish.
Place onion, ginger, garlic and cilantro into a food processor or blender and pulse until veggies are finely chopped. Scrape down sides and add lemon juice, soy sauce, honey and olive oil and pulse a few more times just to combine.
Spoon the sauce evenly over the fish and bake just until cooked through or slightly underdone—about 10–14 minutes, depending on thickness. You can test the doneness of halibut by pressing it lightly with a fork. If the fish ‘flakes’ or separates into layers, it is done. Don’t overcook halibut or it will be dry!
Remove from oven and transfer fish to a serving platter. Allow fish to rest 5 minutes before serving.