Spanish Potato Tortilla

The iconic tortilla española de patatas offers cloudlike chunks of fried spuds and sometimes softened onions suspended in a custard of whisked eggs. Onions are the subject of fiery debate across Spain, where we have the “with-onion” crowd, con-cebollistas, and on the other side, the “without-onion” devotees, sin-cebollistas! Sin-cebollistas either believe in the humility of the potato and consider any interlopers to be flourish, or that onion delivers an unnecess