Heat a deep pot or Dutch oven with 2–3 inches of oil to 350°F over medium heat. Pat the fish fillets dry and season lightly with salt and black pepper on both sides.

In a mixing bowl, whisk together the beer batter mix, Cajun seasoning, and beer until smooth with a thick but pourable consistency. The batter should coat the back of a spoon without being too runny.

Dip each fish fillet into the batter, allowing excess to drip off, then carefully lower into the hot oil. Fry for 4–6 minutes, turning once if needed, until golden brown and the internal temperature reaches 145°F.

Transfer the fried fish to a wire rack and let rest briefly to maintain crispiness. Keep the oil temperature steady between 325–350°F while frying in batches to avoid overcrowding.

Toast the slider buns lightly in a skillet or on a flat top until warm and slightly golden. Spread tartar sauce on the bottom buns, then layer with shredded lettuce, tomato slices, a piece of fried fish, and half a slice of American cheese.

Close the sliders and serve immediately while hot and crispy. Enjoy fresh for the best crunch and flavor.