Carefully remove the cherries’ pits, making sure they keep their round shape. Dissolve the sugar in 1 cup of water and put the syrup to boil until it thickens. Add the cherries, stir slightly and boil to the standard jam density.
During boiling, remove the foam as needed. Before removing from the heat, add the lemon juice and vanilla. While still hot, you can pour the white cherry jam into jars, which you need to close very well.