you don't see nectarine preserves as often as peach preserves, and I think that's a shame. nectarines have a lovely natural acidity, which beautifully balances the sugar required in an old-fashioned preserve. macerating the fruit takes a little longer, but that step helps to break it down, so the jam cooks more quickly and subsequently, tastes fresher. I've included notes at the end of the recipe on how to peel nectarines and how to test for doneness, in case this is your first foray into making preserves.

ingredients
5 pounds firm but ripe nectarines, peeled and pitted, sliced into 1/4 inch pieces
4 cups sugar
1/3 cup freshly squeezed lemon juice

special equipment:
seven 1/2-pint canning jars with lids and screw bands, hot water canner, kitchen tongs, canning tongs, funnel, chopstick or skewer, kitchen towel, saucers

method

1. after peeling, pitting and slicing the nectarines, toss them with 4 cups of sugar in a large bowl. cover and refrigerate for at least 8 hours, or overnight.
2. the next day, sterilize jars and lids, and wash screw bands, according to jar manufacturer's recommendation. chill two saucers for testing the jam.
3. transfer the macerated nectarine mixture to a large pot. the sugar will not be completely dissolved. stir in the lemon juice. bring this mixture to a boil over moderately high heat.
4. stir frequently and simmer briskly for about 20 minutes.
5. reduce the heat and continue to cook the preserves at a slow simmer. stir the mixture frequently to avoid scorching. begin testing jam for the desired thickness after another 15 minutes or so. (see note below)
6. once jam has reached your desired thickness, remove the pan from the heat and set it on the counter.
7. drain your sterilized jars upside down on a clean kitchen towel, and place near the pan of jam. turn them over. using a funnel, ladle the hot jam into each jar, within about a 1/4 inch of the top of the jar.
8. insert the chopstick or skewer into each jar of jam, moving it gently through the preserves to get rid of any air pockets.
9. using a clean, damp towel wipe the tops of the jars. use the kitchen tongs to center the lids on the jars. add the screw bands and tighten.
10. this amount of nectarines usually makes seven 1/2-pints of jam, but yields can vary depending on the amount of liquid in the fruit. I usually sterilize an extra jar, just in case. if you have a last jar that isn't full, seal it and let it cool but don't process it in the hot water canner. you should just refrigerate it, and use it first.
11. add the full jam jars to the hot water canner and bring the water back to a boil. process the jam for 10 minutes in the boiling water.
12. remove the processed jars from the hot water canner, and place them on a kitchen towel on the counter to cool.
13. as the seals set on the jars, you should hear a "ping." if you don't hear this sound, don't worry. it's most important that the lids are concave on the jars.
14. an easy way to tell that the seal is set is this: once the jars are processed and cooled remove the screw band from one and see if you can get the lid off. it should be difficult to do this. if the lid comes off easily, the seal didn't set. don't panic! you can just refrigerate the jam and use it first. jarred but unprocessed jam can last in your refrigerator for several months.

this jam tastes best if you let it sit at least a day for the flavors to develop. I usually squirrel away a couple of jars for the dead of winter and when the rain starts to get to me, I pop one open and remember the summer sunshine.

notes
to test jam for desired thickness: drop a small spoonful of jam onto a chilled saucer, refrigerate for a minute, then tilt the plate. the jam should stay mounded, not run. if you swipe your finger through the jam, it should leave a trail through the preserves. ask yourself, doe this look like jam? if the mixture is still thin and watery, place the pan back on the burner and cook for another minute or so, and then retest.

to peel nectarines: prepare a bowl with an ice bath (a mixture of ice and cold water). bring a large pot of water to a rolling boil. while the water is heating, use a paring knife to score a small "x" on the bottom of each nectarine. when the water is boiling, plunge the whole fruit into the boiling water, then immediately into an ice bath. when they're cool enough to handle, slip the skins right off. I usually plunge two or three fruit into the hot water and then into the cold water, and peel them in batches. you can use this method with peaches and tomatoes too!

want to learn more about preserving and canning safely? check out the USDA Complete Guide to Home Canning