Blend flour, baking powder, and salt; set aside. Beat together egg, milk, and oil and stir into flour/salt mixture. Heat frying oil in a deep pan to about 375 ( watch to make sure it's not too hot - it should not start smoking ). Dip onion rings a few at a time into the batter, drop into hot oil and turn over as they brown, this should only be a couple of minutes or less per side. When rings are a light golden brown in color, lift out and drain on paper towels. Salt rings and serve hot.