I made these for Cinco de Mayo, and they were muy excellente! My bf said he never understood the big deal about fish tacos until he tasted these! Delicious, light and flaky fish with a lemon sour cream and cabbage on top.
For the Beer Batter: Mix the flour, salt and pepper in a medium bowl. Gradually add in the beer while whisking. Set aside and let the batter rest for 15 minutes before using.
For Cream Sauce: Add the mayonnaise and sour cream to a medium bowl. Whisk in the lemon zest, lemon juice and water. Season, to taste, with salt and pepper (can be made 3 days ahead, covered and refrigerated).
For the Fish: In a large skillet, over medium heat, add enough oil to reach a depth of 1-inch. Heat the oil until a deep-fry thermometer registers 350 degrees F or when the end of a wooden spoon sizzles when inserted into the oil.
On a large plate, combine the flour and salt. Season the fish pieces all over with salt and pepper and coat with the flour. Working in batches, dip the fillets in the beer batter and coat on both sides. Fry in the hot oil until golden brown and cooked through, about 5 minutes. Transfer to paper towels to drain.
Make tacos with the tortillas and fish and top each with cream, shredded cabbage, salsa and guacamole, if desired.