1 Rinse, taste, and prep the fruit: Rinse the fruit. If you working with stone fruit, take out the pits, chop the fruit. If working with apples or pears, peel and core them, then chop. If working with grapes, de-stem them.
Taste the fruit before proceeding. Note how sweet the fruit is. If very sweet (ripe Concord grapes for example) you will not need to add any sugar. If still a little tart, you may need to add some sugar in the next step.
2 Cook fruit with water, sugar, lemon juice, spices: Place fruit in a large saucepan. Add a half cup of water for every 4 cups of chopped fruit.
Bring to a simmer, cover and let cook on a low heat for 10-15 minutes, or until the fruit is cooked through. Uncover and stir.
Use a potato masher to mash up the fruit in the pan.
Taste the fruit and determine what and how much sugar, lemon juice, or spices to add.
Add sugar in small amounts (1 Tbsp at a time if working with 4 cups of fruit), to desired level of sweetness.
Add lemon juice one teaspoon at a time to help brighten the flavor of the fruit. Add a pinch or two of cinnamon, nutmeg, or other spices to augment the flavor.
Continue to simmer and stir until any added sugar is completely dissolved and the fruit purée has thickened, another 5 or 10 minutes (or more).
Note if you are working with grapes - strain the juice out of the mashed grapes to make grape juice. Force what is left behind, after straining, through a food mill, to make the purée for the next step.
3 Purée the cooked, mashed fruit: Put the purée through a food mill or chinoise. Alternatively purée it thoroughly in a blender or food processor.
Taste again and adjust sugar/lemon/spices if necessary. The purée should be very smooth.
4 Pour purée into lined baking sheet: Line a rimmed baking sheet with sturdy plastic wrap (the kind that is microwave safe). Pour out the purée into the lined baking sheet to about an 1/8 to 1/4 inch thickness.
5 Slowly dry out in oven at a very low temp: Place the baking sheet in the oven, try to keep any plastic wrap from touch the sides of the oven or the oven racks. Also try to make sure that the plastic wrap hasn't folded back over on top of the purée. If this happens, the purée won't dry out.
Heat the oven to a low 140°F. If you have a convection setting, use it, it will speed up the process and help dry out the purée. Let dry in the oven like this for as long as it takes for the purée to dry out and form fruit leather.
We usually keep it in the oven overnight, so about 8-12 hours. The fruit leather is ready when it is no longer sticky, but has a smooth surface.
Alternatives to the oven. If you have a food dehydrator, this would be a great use of it. My mother suggested putting the tray in the weber grill, and leaving covered, in the sun all day. Sounds like a good trick, but I haven't tried it yet.
My parents remember the traditional way of making fruit leather was just to tent the tray with some cheesecloth and leave it outside in the sun on a hot day.
6 Roll up in its plastic wrap to store: When the fruit leather is ready, you can easily peel it up from the plastic wrap.
To store it, roll it in its plastic wrap, put it in an airtight container and store in the refrigerator or freezer.