In a bowl mix flour, baking powder, lime zest, salt, black pepper, chili powder, cayenne, lime juice and beer together.
Heat oil in a skillet to 360 F˚.
Season fish evenly with salt, pepper, chili powder and cayenne. Cut into 3 inch strips. Dredge strips 3 at a time. Then fry.
Fry fish for 4 minutes turning occasionally until evenly golden brown.
For cilantro sauce place all ingredients in a food processor and blitz for 30 seconds to 1 minute.
Assemble taco, fish, cabbage, sauce, jalapeno slices and cilantro.