Start heating your oven to 240 C / 475 F / Gas Mark 9.
Chop the tomatoes.
In a casserole dish, put the olive oil, tomatoes, red onion, sugar, thyme. Stir a bit to blend it all. Season with salt and pepper.
Roll out the puff pastry to fit the dish. Place overtop the tomato mixture. Cook until pastry is puffed and golden -- 15 to 20 minutes. Turn upside down on a plate, so that you are serving it with the tomatoes on top. Serve hot, pizza style.
Notes
You want 1 sheet of puff pastry, thawed. Frozen puff pastry takes about 2 hours to thaw on the counter.