Step 1

Place the butter in a heavy-bottomed, 12-inch (30cm) heatproof pan. Transfer to the oven and cook until the butter is melted, about 4 minutes.

Step 2

Remove the pan from the oven and add the tomatoes to the melted butter, placing the halved ones cut-side down and scattering the smaller ones around and between the cut tomatoes. Don't skimp; it may look like there are too many tomatoes but they'll soften and shrink as they cook down.Sprinkle the vinegar, sugar, salt, and thyme over the tomatoes.

Step 3

Transfer to the oven and cook for 10 minutes.

Step 4

While the tomatoes cook, prepare the pastry: Place the sheet of pastry on a work surface. Use a sharp knife to cut into a 12-inch (30m) circle. You don’t need to cut an exact circle; you’re going to tuck all the excess bits in later anyway.

Step 5

When the tomatoes have softened, remove the pan from the oven. Working quickly, lay the pastry over the top of the warm tomatoes and tuck the edges down all around. Cut a small vent in the centre of the pastry to release steam, then put the pan back in the oven and cook until the pastry is puffed and golden brown all over, 15 to 20 minutes.

Step 6

Remove the tart from the oven and let it sit undisturbed for around 30 minutes to cool slightly. Put a large plate upside down over the top of the pan. Use a folded kitchen towel or oven mitts to make sure you’re holding everything safely, then flip it over and invert the tart onto the plate. Lift off the pan to reveal your beautiful creation. I like to give the bottom of the pan a sharp tap with a wooden spoon before flipping to encourage all the tomatoes to come out, but if any bits remain, just lift them out with a spatula and place them back on the tart after you’ve turned it out.Slice into wedges and serve warm.