Prepare a large pot of boiling water. With a paring knife, cut a small "x" in the bottom of each peach. Working with a few peaches at a time, place them in the boiling water for 1-2 minutes, until the skins begin to peel back from the "x". Remove from the pot.
Use your fingers to peel away the skins, starting with the "x" at the bottom. Slice the peaches and discard the pits.
In a large saucepan, combine the peaches, sugar, and lemon juice and place over medium high heat. Stir to dissolve the sugar and use a mashing utensil to break of the slices into smaller pieces. Bring the jam to a boil, then let simmer until thickened, stirring frequently and skimming away any foam from the surface.
The jam will thicken in about 45-60 minutes. Test jam by pouring a teaspoon onto a very cold plate (placed in the freezer for 15 minutes). Wipe your finger through the jam. Jam has reached the proper consistency when it holds its shape and does not run to fill the gap created by your finger.
During the last 15 minutes of cooking, add the amaretto. Meanwhile, bring a large pot of water to a boil and place your canning jars and lids inside. Let boil for several minutes.
Remove the jars and lids from the water. Spoon the jam into the jars, leaving a ¼-inch headspace. Use a clean damp towel to whip the rims of the jars. Place the lids and screw on the rings, and use a jar lifter to lower into the boiling water. Let the water return to a boil, then continue to boil for 10 minutes (see note below).
Remove the processed jars from the water and let cool to room temperature. Remove the rings from the jars and store in a cool place out of direct sunlight and for best results, use within a year.
Note: Can also be stored in the freezer for several months if you prefer not to can.