Spray a baking dish with cooking spray. Place red snapper skin-side down in the baking dish. Sprinkle evenly with garlic, garlic salt, and red pepper. Spread cilantro evenly over the fish; squeeze lime evenly on top.
Marinate in the refrigerator, 30 minutes to 1 hour.
Preheat the oven to 425 degrees F (220 degrees C). Melt butter and pour evenly over the fish.
Bake in the preheated oven until flesh flakes easily with a fork, 15 to 18 minutes. Serve with juices spooned over the fish, if desired.
