What qua tart?

It seems like there might be a typo in your question. If you meant "What is a tart?" a tart is a type of pastry dish with a shallow, open top and a filling, which can be sweet or savory. Sweet tarts often contain fruits, custards, or creams, while savory tarts might include ingredients like vegetables, cheeses, or meats. If you meant something else, please clarify!