In a large bowl whisk together the flour, corn starch, beer and salt and pepper until combined. Let stand at room temperature for 15 minutes before using.
In a separate large bowl add in the sour cream, avocado, lime juice, lime zest, salt and pepper, and mash with a hand masher until completely smooth. Keep cool before serving.
Next, dip the tilapia in the batter and completely coat. Place the coated tilapia into a deep fryer on 375° for 4 to 6 minutes or until golden brown and cooked through out. Once cooked remove fro the fryer and let dry for 1 minute.
To Plate: Place down a corn tortilla and add on 1 piece of beer battered and fried tilapia, 1 to 2 tablespoons of avocado lime sauce, a small amount of sliced red cabbage, a few sliced radishes and garnish with fresh cilantro leaves.