- Preheat the oven to 300 degrees. Cut the ends off the tomatoes, then cut in half. Lay the tomatoes out on a sheet tray, with the cut side facing up. Sprinkle with salt and pepper. Place in the oven and bake for about 2 hours, or until the tomatoes start to look shriveled and a little brown. Let cool. The tomatoes are now ready to use. You can also bag them up in plastic freezer bags and freeze.