Combine the thyme, shallots, garlic and three tablespoons of olive oil.
Stand one hour. Preheat the oven to 160 degC.
Halve the tomatoes lengthwise and place, cut side down, in a shallow baking pan.
Drizzle with the remaining oil and sprinkle with salt and pepper.
Roast for 20 minutes. Carefully flip over and dot the thyme mixture over the top.
Continue roasting for 15 to 20 minutes.