Pit washed cherries, then chop about 1/2 or 1/3 of them into rough pieces, and leave the others whole. Add all the cherries to a medium pot along with the lemon juice.
Cook over medium heat, until bubbling, then continue to cook while stirring occasionally for about 20-25 minutes. Make sure you stir especially towards the end of that time so the juice on the bottom does not burn.
While cooking, use a spoon to smash the whole cherries to release the juice and flatten them
After the cherries are fully cooked, add the sugar, stir to mix it in and dissolve it, then continue to cook over medium-high heat for another 5-7 minutes. (Again, be sure to stir, so the sugar and cherries don't burn.)
After cooking, the juice should have started to 'gel' a bit and thicken so that it starts to coat the back of your spoon or ladle. Remove the preserves from heat, and test if they are done. If the preserves are not done, return them to the heat and cook them for a few more minutes, then test them again. When done, let the preserves cool slightly, then transfer it to jars.
Once they are cooled, they will keep refrigerated for several months.