Begin by peeling and slicing onion into ¾ inch thick rings. Separate into individual pieces.
Submerge onion slices in buttermilk or milk/sour cream mixture. Allow to soak for 30 minutes or more.
Meanwhile, in a shallow bowl mix flour and baking powder with salt and pepper and BBQ rub.
Heat oil in heavy Dutch oven pan until very hot. A thermometer placed in the oil should read 350* or higher.
Prepare a plate or tray with layers of paper towel for draining fried onion rings.
Prepare a plate or tray with layers of paper towel for draining fried onion rings.
To cook, begin by removing onion rings from milk mixture, tossing in seasoned flour, dipping again in egg/milk mixture and returning to seasoned flour.
Fry in prepared oil until golden brown, turning once. You can fry a few at a time, cooking in batches.
When golden brown, drain to paper towel and immediately season with salt and/or BBQ rub. Set aside.