Begin by taking your yellow onions and slice them into rings roughly 1/4 inch thick.

In a mixing bowl, whisk together the sourdough discard, baking powder, and seltzer water until the mixture reaches a thin pancake batter consistency.

Lightly coat each onion ring in all-purpose flour, shaking off any excess.

One by one, take the flour-coated onion rings and dip them into the batter, ensuring they are well covered.

In a deep fryer or a sturdy pot, heat the oil to between 350°F and 375°F.

Carefully add the battered onion rings into the hot oil in small batches. Fry them for about 3-5 minutes.

Once cooked, remove the onion rings from the oil and place them on a plate lined with paper towels to drain excess oil.