Oil, for frying
2 large sweet onions, cut into 1/2-inch thick rings, thin skins removed
1 1/2 cups rice flour, plus more, for dredging
1 tablespoon baking powder
1 tablespoon baking soda
1 egg yolk
3/4-1 cup beer (use enough until you get thick pancake batter consistency)
1/2 teaspoon salt, plus more for seasoning
Freshly ground black pepper
Fill a large Dutch oven or fryer with 1 1/2" of oil and preheat to 350 degrees F.
Sift dry ingredients into a large mixing bowl and make a well in the center. Crack the egg yolk into a separate bowl and break it up with a fork. Add this to the well in the middle of the flour and slowly pour in the beer as you whisk. Gradually make wider circles with the whisk to incorporate the dry ingredients from the edges - this will minimize the chance of lumps. Continue until all the dry ingredients are mixed and the batter is of a smooth consistency.
In a large dish add some rice flour, and season with salt and pepper, to taste. Coat each ring in the flour. Dip in the batter and fry in hot oil in batches until golden. Drain on paper towels and season with salt.