In a large mixing bowl, combine all-purpose flour, baking powder, salt, and black pepper. Gradually whisk in the cold beer until you achieve a thick and smooth batter without lumps, approximately 2-3 minutes.

In a deep fryer or a large, heavy pot, pour enough oil to submerge the onion rings, typically about 3 inches deep. Heat the oil to 375°F (190°C), using a thermometer for accurate measurement.

While the oil heats, take your prepared onion rings and dip them one at a time into the beer batter. Make sure each ring is well-coated, allowing any excess batter to drip off.

Carefully add the coated onion rings to the hot oil in batches, ensuring not to overcrowd the pot. Fry them for 3-4 minutes, or until they turn a lovely golden brown and float to the surface.

Once golden brown, use a slotted spoon to remove the Beer-Battered Onion Rings from the oil. Place them on a plate lined with paper towels to absorb any excess oil.

Serve your hot and crispy Beer-Battered Onion Rings immediately, accompanied by your choice of delicious dipping sauces like ranch, ketchup, or aioli.