Cut tomatoes in half and remove the stem end. Scoop out the inside of the tomatoes in to the bowl of a food processor (seeds and pulp). Arrange tomatoes on a parchment lined baking sheet, cut side up. Pre-heat oven to 275° F.
To the food processor with the tomato insides, add the garlic, olive oil, balsamic, tomato sauce (or juice) and a bit of salt and pepper. Spoon this mixture into the hollowed out tomato halves, filling them about 2/3 full. (You may not use it all). Sprinkle the tops with a few fresh or dried thyme leaves.
Bake in the preheated oven for 1 1/2-2 hours, or until the liquid in the middle has reduced and is just tacky to the touch (mine took 2 hours).
Can be stored in the fridge for 7-10 days or freeze them.