To make oven-dried tomatoes, cut 2 pounds of plum tomatoes in half lengthwise, place them cut side up on a baking sheet lined with parchment, season with salt and let the tomatoes stand for approximately 20 minutes. Put the tomatoes in the oven, and roast them at 250 degrees Fahrenheit for about four hours.
Alternatively, cut 8 to 10 plum tomatoes and a total of 8 to 10 red, yellow, green or orange tomatoes in half. Arrange them cut side up on a cookie sheet lined with parchment. Space the tomato halves so that enough room remains between them for the heat in the oven to circulate around and between them.
Sprinkle the tomatoes with 1 tablespoon of sugar, add salt and freshly ground black pepper to taste, and sprinkle any other herbs of your choice, such as basil, rosemary or oregano. Bake the tomatoes for 90 minutes to six hours at 250 degrees Fahrenheit, or until the pieces shrink slightly, the edges shrivel and the juices stop running.
The total cooking time depends on the heat of the oven and the ripeness of the tomatoes. Generally, plum and paste tomatoes that are ripe but not overripe work best. However, another option is larger, round tomatoes, such as beef or heirloom varieties, cut crosswise into slices that are no more than 1/4-inch thick.