I have in my oven at the moment, 8 sliced heirloom tomatoes slowly releasing their sweet smell as they very slowly “oven-dry” for 2 – 3 days.
By that I mean, I cut the tomatoes in 1/2 (or sometimes 1/3rds if they are big).  I then lay them on a silicone mat on a baking tray and sprinkle them with olive oil, salt and freshly ground pepper, then sprinkle chopped fresh thyme,  garlic, marjoram and a spray of balsamic vinegar on them.
The oven has a pilot light, so is always warm, but I set it to 200 degrees or the lowest it will go and leave them in for 2 -3  days, checking on them from time to time.

They are wonderful in pasta dishes or sandwiches and store so well in the fridge.