Place the catfish fillets in a wide bowl and cover with the buttermilk or milk. Let it soak for about an hour (although even 30 minutes will improve the flavor).

Remove the fillets from the milk and dredge them in the cornmeal. Pat them on both sides to make sure the cornmeal coating adheres well.

Fry the fillets in about an inch of moderately hot oil, about 5 minutes per side, until nice and golden brown. Serve hot with lemon wedges.