Mix the flour (or flour and cornmeal) in a bowl and stir in the beer, black and red pepper, and salt. Cover, and let sit one hour at room temperature.
In a wide saucepan or skillet, heat about 2 inches (5 cm) peanut oil until it reaches 370ºF (180ºC.)
Spread some flour on a plate and working in batches, toss 5 or 6 of the onion rings in the flour, then dip each one in the batter, shaking off any excess, then dropping them one at a time into the hot oil.
Cook the onion rings for a few minutes, turning them with a slotted spon or other utensil with holes, until browned on both sides. Remove and set on paper towels, or on a wire cooling rack above paper towels, to drain. While warm, salt the onion rings with additional salt. Continue to fry the rest of the onions the same way. Eat immediately.