In a large, heavy saucepan, combine 1 tablespoon cornstarch per 6 tomatoes reduced to a puree in a blender. Cook over medium heat until thick, 10 to 15 minutes. Remove from the heat and let cool.
Pour 1 cup of puree per leather in strips on a drying sheet set in a dehydrator tray. Slap the tray on the counter a couple times to level the liquid. Dehydrate at 125°F (52°C) until the leathers easily peel off the drying sheet, about 10-12 hours. When dehydrated, it will be brittle, feel dry, and break apart easily in your hands. Store in canning jars or vacuum seal with an oxygen pack and double-bag in Mylar.
Take one leather, place it in a small heatproof bowl, and pour 1 cup boiling water over it. Let sit 15 to 20 minutes. One leather will make 1 cup tomato puree.
