Salt the tomato halves and leave to sit for approx. 20 mins. Place the tomatoes in a sieve, drain. Mix the tomatoes and thyme, season. Sprinkle the sugar onto the prepared baking paper.
Caramelize for approx. 5 mins. in the centre of an oven preheated to 220 °C until the sugar turns a light brown colour.
Remove the tin from the oven. Place the butter on top of the caramel, melt. Top with the tomatoes and shallots. Firmly prick the pastry with a fork and lay loosely over the vegetables. Carefully tuck the edges down the inside of the tin.
Bake in the centre of a preheated oven for approx. 20 mins. Remove and leave to stand for approx. 10 mins. Turn out the tarte tatin onto a round platter or dinner plate. Carefully peel away the paper.