In a food processor, combine the flour blend, corn flakes, baking powder, paprika, garlic powder and 1½ teaspoons salt. Add the beer and egg whites; whisk until smooth. Cover and refrigerate for 15 minutes.
Meanwhile, stir together the mayonnaise, lemon juice and zest, mustard and capers; season with salt and pepper.
Fill a large pot with enough oil to reach a depth of 1 inch and heat over medium-high heat until it registers 350° on a deep-fat thermometer. Working in batches, lightly dredge the fish strips in
the flour blend, then coat with the batter. Fry, turning once, until golden brown, 3 to 4 minutes total. Remove with a slotted spoon and drain on paper towels; season with salt. Serve with the tartar sauce.