Prepare a boiling water bath canner and enough jars to hold five half pints (the yield will be somewhere between 4 and 5 half pints).
Place the pitted cherries in a pan that holds at least five quarts (these cherries will foam a lot) and add the sugar and lemon juice. Stir to help the sugar dissolve.
Once the contents of the pan look juicy, place it on the stove over high heat.
Bring the cherries and their liquid to a boil and let them cook at a good clip for 5 to 6 minutes, until cherries soften a little and the liquid in the pan as thickened a bit. Add the almond extract.
Remove pan from heat, funnel cherries and syrup into prepared jars, leaving 1/2 inch headspace. Use a wooden chopstick to remove any trapped air bubbles and adjust the headspace as is necessary. Wipe the rims, apply the lids and rings, and process in a boiling water bath for 10 minutes.
When the time is up, remove the jars and set them on a folded kitchen towel to cool. When the jars have cooled enough that you can comfortably handle them, check the seals. Sealed jars can be stored at room temperature for up to a year. Any unsealed jars should be refrigerated and used promptly.