In a large bowl stir together the flour, cayenne, garlic powder and salt.
Add the egg and the beer, stir with a fork until well combined.
Add about 2 inches of oil to a skillet over medium high heat (ideally you want to oil to stay around 350 degrees).
A few at a time, dip the shrimp into the batter, let the excess batter slide off, then add to the oil. Allow the shrimp to cook until golden brown, about 2 minutes on each side. Remove from pan and add to a stack of paper towels.
In a small bowl stir together the crema, chipotle chili and lime juice.
Add the shrimp to the tortillas, top with diced onions, cilantro and chipotle crema.