Plum tomatoes Rock Salt Olive Oil Rosemary Dried chilies Wash, halve and seed fresh plum tomatoes. Place on racks and bake in a 175 F (80 C) oven until wrinkled and dry, 16 to 18 hours. Sprinkle a thin layer of rock salt in the bottom of a jar. pack in the tomatoes and cover with olive oil, making sure the tomatoes are completely immersed. Add a sprig of rosemary or a couple of dried chilies to the oil, if desired. Store in the refrigerator for one month before using. Scatter the tomatoes into pasta sauces, chop them finely with olives for a salsa to serve with fish or mix them with cream cheese to make a spread for crackers. You can also give them away as gifts. Sun-dried tomatoes last indefinitely in the refrigerator.