The best tip for roasting tomatoes is to eye up your favourite roasting or baking tray and buy as many tomatoes as it takes to fill it. Halve them top to bottom and scoop out the seeds with a spoon and discard, leaving a hollow bowl of tomato flesh.
Lay these close together, cut side up, and give them a pretty generous glug of olive oil, a scant sprinkling of sugar and a little more generous pinch of salt. You could also add a herb such as thyme or oregano.
Preheat the oven to 140°C/fan120°C/gas 1 and cook the tomatoes for 2 hours or so. If you have an old-fashioned oven with a pilot light, you could leave the tomatoes in the oven overnight. The tomatoes are ready when they look wrinkly and a little dry.