I just dehydrate spaghetti sauce until it's a leather -- just like fruit leathers. I don't even boil it to rehydrate it. Just pour the desired amount of water over it and let it sit for an hour or so, then heat it up. One suggestion: don't vaccum-seal tomato leathers in your FoodSaver. It compacts the leather into a hard, almost impossible-to-rehydrate clump.
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