In a small bowl, whisk together the melted butter, garlic, red pepper flakes, lemon juice and lemon zest; set aside.
Season the catfish with salt and pepper to taste. Place the fish in a single layer into a 9 x 13-inch baking dish. Scatter the lemon slices over the top of the fish. Spoon the lemon butter mixture over the stop of the fish.
Bake until the fish cooked through and easily flakes with a fork, about 10 to 12 minutes.
Serve immediately, garnished with parsley if desired.
