Drain the cherries on a sieve and collect the juice. Peel the hot washed lemon thinly in a spiral and stir the cornstarch with a little juice until smooth.
Bring the remaining juice to the boil, pour in the starch while stirring and bring to the boil again. Fold in the cherries and let everything cool down, remove the lemon peel.
Mix the sour milk (or yoghurt or sour cream) with the sugar and season with the cinnamon. Fold in the whipped cream and serve on plates with the cherry compote.
Sprinkle some cinnamon on top and serve immediately.