Place onion in resealable plastic bag with 1 teaspoon salt, basil, and oregano. Squeeze in juice from 1 1/2 limes. Add enough water to help spread marinade all over the onion slices. Seal and refrigerate, 8 hours to overnight.
Combine sour cream, mayonnaise, and the juice of 1 lime in a bowl. Mix, adding more lime juice as needed, until the white sauce is runny. Cut the remaining limes into wedges.
Heat oil to 350 degrees F (175 degrees C) in a deep pot over medium heat.
Preheat the oven to 225 degrees F (110 degrees C). Place tortillas in oven to keep warm.
Whisk flour, beer, and egg together in a medium bowl until texture resembles pancake batter. Dip 3 to 4 pieces of fish into the mixture and fry in the hot oil until golden brown, 2 to 3 minutes. Drain on paper towels. Repeat with remaining fish.
Place fried fish over warmed tortillas, topped with the marinated onions, white sauce, lime wedges, cabbage, pico de gallo, and cilantro.
Any variety of white fish will do. You could also use already breaded fish.
This recipe can be baked instead of fried.
We have determined the nutritional value of oil for frying based on a retention value of 10% after cooking. Amount will vary depending on cooking time and temperature, ingredient density, and specific type of oil used.
Per Serving: 674 calories;57.3 g fat;
30.6 g carbohydrates;
10.8 g protein;
35 mg cholesterol;
411 mg sodium.