To make sweet onion ring batter, prepare sliced onions and other main ingredients including egg, flour, salt and buttermilk. Mix all ingredients well to make batter, and dip sliced onions into that batter. Heat the oil to at least 360 degrees Fahrenheit, and fry until the onions turn golden brown. Drain the onions on paper towels, then enjoy.
Batter for two large sweet onions requires 3 cups of buttermilk, 2 cups of all-purpose four, two eggs and 2 teaspoons of salt. Adding 1 cup of finely ground cornmeal results in a subtle change in mouth feel and flavor. To make the dish a bit spicy, add 1/4 teaspoon of cayenne pepper. Slice the sweet onions thinly enough to flash-fry but thick enough to let the onion flavor shine through.
Mix the ingredients in two wide shallow bowls. In the first bowl, whisk together flour, cornmeal and cayenne pepper. In the second bowl, beat egg and buttermilk. Reserve half the flour mixture so when the first batch starts to get wet and gummy, you can replace it with the remaining half.
Handle the coating process delicately. Toss the onion rings in the flour mixture, then dip them into the buttermilk mixture. Let the liquid drip off, then toss them again in the flour mixture. Shake off the flour before placing the rings into the hot oil. Let as much liquid and then as much flour fall off as possible; less breading means less grease absorption and a crisper finished product.