Step 1 Heat the oven to 200 degrees.
Step 2 Prepare the tomatoes: Score the skin at the base of each tomato with an X. Place the tomatoes in simmering water just until the skin starts to pull away at the base, about 30 seconds. Immediately remove the tomatoes and place in a bowl of ice water to stop the cooking process. When the tomatoes are cooled, peel the skins and halve the tomatoes crosswise (across the equator), then de-seed.
Step 3Choose a pan in which the tomatoes will fit in a single layer. Cover the bottom of the pan with a layer of olive oil, and place the tomatoes in the pan cut-side down. Place a half clove of garlic on each tomato half, along with a branch of thyme and half of a bay leaf. Season the tomatoes with a sprinkling of salt and pepper, then drizzle a little more olive oil over the tomatoes.
Step 4Place the tomatoes in the oven and cook for 3 to 4 hours. Baste the tomatoes with the olive oil every hour. The tomatoes will dry and intensify while in the oven.
Step 5When the tomatoes are done, remove them from the oil and place them on a plate, then put them in the refrigerator to cool.
Step 6When the tomatoes are cool, place them on a cutting board and finely chop them with a sharp knife. Place the tomatoes in a mixing bowl, and taste them for seasoning. Season with lemon zest and more salt and pepper if needed.