This recipe adapted from Thomas Keller's "Bouchon" (Artisan, 2004)
Preheat oven to 250 degrees. Bring a large saucepan of water to a boil. With a sharp paring knife, cut out and discard stem end of each tomato; score opposite end. Place tomatoes in a large bowl.
Pour boiling water over tomatoes; let sit until skin is easily peeled, about 15 seconds. Drain tomatoes, and cover with ice.
Peel tomatoes when cool enough to handle. Halve lengthwise and place, cut-side up, on a parchment paper-lined baking sheet. Drizzle with olive oil; season with salt, pepper, and thyme.
Roast until tomatoes are dried halfway through, about 5 to 6 hours. Let stand until cool. Transfer tomatoes to a storage container; pour oil from baking sheet over the top. Refrigerate for up to 1 week.