When you spot a good deal on plum tomatoes, buy a bunch. Roasting preserves them for later use and maximizes their sweetness. Use roasted tomatoes in Roasted-Tomato Pasta with Basil, Beef and Tomato Stew, and Spiced Tomato Soup.
Preheat oven to 450 degrees. Divide tomatoes and thyme between two shallow baking pans or rimmed baking sheets. Toss with oil; season with salt and pepper. Bake until tomatoes burst, 45 minutes, rotating pans halfway through. Let cool, then coarsely chop.