Put the cherries in a saucepan with the water and honey. Tie the rosemary sprigs together with kitchen thread. Bring everything to the boil until the cherries burst. Then take out the rosemary and mix the cold bowl.
Season to taste with a little lemon juice and chill. Just before serving, stir in the sour cream with a whisk. Possibly add a little sugar to taste.
You can also use sour cherries instead of sweet cherries, but then you should use more honey or sugar.