Preheat a deep-fryer to 375℉ (190℃). Or fill a large saucepan ⅓-½ full with vegetable oil and heat to 375℉ (190℃). There should be a good 3-4 inches of space to prevent it from spilling over when you add the fish.
Use the fillets whole or cut them into bite-sized pieces—season as desired.
Beat the eggs and buttermilk in a separate bowl. Then, pour it over the fish and coat well.
Mix the cornmeal, granulated garlic, onion powder, cayenne, salt, and pepper in a shallow bowl.
Drain the excess buttermilk mixture from the fish. Then coat each piece with the cornmeal mixture.
Fry the fish a few pieces (whole fillets or nuggets) at a time, moving them around so they don't stick, until brown and crispy. It usually takes 3-4 minutes per side, depending on the size. (The large fillets took 6 minutes per side.)
Remove from the hot oil with a slotted spoon. Place them on a baking rack to drain excess oil and ensure crispness. Repeat with the remaining fillets.
Serve the fish with lemon wedges and spicy tartar sauce.
For the sauce: combine mayonnaise, garlic, hot pepper relish, onions, mustards, hot sauce, salt, and pepper in a serving bowl. Cover with plastic wrap and let the flavors mellow in the refrigerator for at least an hour before serving.