Wash the cherries and remove the seeds.
Put the ingredients into a frying pan without any oil and turn on the heat. When the sugar dissolves, add the cherries and simmer for about 5 minutes.
Dissolve the cornstarch and lemon juice in water, then add to the pan. Simmer until thickened. Then, add the Kirschwasser.
The sauce is done.
Bring the butter, egg, and milk to room temperature. Combine the flour and baking powder and sift. Line the muffin tin with paper cups.
In a bowl, knead the butter until creamy, then add the sugar and mix well. Preheat the oven to 180.
Add a little bit at a time of the beaten egg and milk into the bowl from Step 6, mixing well with each addition.
Add the sifted dry ingredients to Step 7, folding without kneading, until no longer powdery.
Add the cherry sauce from Step 4 to Step 8 and combine evenly.
Spoon the batter into the muffin tin and smooth the surfaces. Bake at 180 for 30-35 minutes. Cover with aluminum foil along the way. Check with a skewer or toothpick to see if it's done.
Let cool, then remove from the muffin tin. Continue cooling on a rack. When you cut it in half, it looks like this. It's full of cherries.