What is the persistent, lighthearted argument concerning Tortilla Española preparation?

Answer

Whether it should include onions (con cebolla) or not (sin cebolla)

A widely recognized and ongoing lighthearted culinary debate throughout Spain concerns the composition of the Tortilla Española, the staple potato and egg dish. The core of this argument revolves around the inclusion of onions. Proponents of the *sin cebolla* (without onion) style advocate for a pure flavor profile of potato and egg, while those supporting *con cebolla* believe the onion adds necessary moisture and sweetness to the mixture. While often relegated to tapas or sandwich fillings, a thick, freshly made tortilla can serve as a main course anchored by a salad.

What is the persistent, lighthearted argument concerning Tortilla Española preparation?
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