Savory Delight: Cheesy Caramelized Onion Tart Recipe

This recipe for a cheesy caramelized onion tart combines the rich, buttery, and sweet flavors of caramelized onions with Swiss cheese, Parmesan, and chives. The onions are slowly cooked until soft and browned, then placed on a puff pastry sheet and topped with cheese before baking. The tart can be made ahead of time or served at room temperature, and the recipe is customizable with different types of onions, cheeses, and herbs.