In a large bowl, whisk together the flour, cornstarch, Cajun seasoning, salt, and black pepper.
Gradually whisk in the beer until the mixture is smooth and well combined.Score the skin side of each Acadian Redfish fillet lightly to help the batter adhere.
Pat the fillets dry with paper towels to ensure a crispy coating.
In a large skillet or deep pot, heat the oil over medium-high heat until it reaches about 350°F (175°C). You can test the oil by dropping in a small amount of batter; it should sizzle and rise to the surface.
Dip each fillet into the batter, ensuring it’s well coated. Allow excess batter to drip off. Carefully place the battered fillets into the hot oil, a few at a time to avoid overcrowding. Fry for about 2-3 minutes on each side, or until golden brown and crispy.
Use a slotted spoon to remove the fish and place them on a paper towel-lined plate to drain excess oil.
Serve hot with tartar sauce, lemon wedges, and your choice of sides like French fries or coleslaw.