For the achiote butter: Mix everything in a food processor until well combined.
For the corn salsa: Mix everything in a bowl and season with salt and pepper.
For the tamales: Cut banana leaves into approximately 12-inch squares and wipe clean with damp towel. Place about 3 ounces of prepared tamale masa in the middle of the leaf and place a piece of fish on top of the masa. Coat the fish with achiote-chile butter then top with another spoonful of masa and spread over the fish to completely encase. Fold the edges of the banana leaf over the fish, making a packet. Tie with a string and steam for 10 minutes. Serve with Corn Salsa.