Red Onion, Tomato, Pesto and Mozzarella Tart

I tend to think of tarts as spring/summer dishes, but recently had an urge to make a puff pastry dish. This is a pretty straightforward tart to make and tastes great hot or cold; I was lazy and bought pre-rolled puff pastry so all I had to do was assemble and cook. I added the mozarella after the tart had been cooked, as I really love uncooked mozeralla, but you could just add it to the top before baking if you prefer. I also used a mixture of large tomatoes and cherry tomatoes; cherry tomatoes have a nicer taste, but take a lot more time to prepare.