Melt cane sugar in a saucepan over low heat.
When the sugar has melted, add the butter and stir.
Add the cherries to the caramel and cook it for 5-7 minutes over low heat. The result should be a thick jam. Remove it from the heat and cool.
While the cherry jam is cooling, mix the mascarpone cheese and sour cream in a deep bowl.
Whip everything until smooth. You should get a thick cheese cream.
Add cherry jam to the cheese cream and stir.
Cut the sponge cake into three equal parts. Grease two of them with cheese and cherry cream.
Stack the cakes. There should be an empty cake on top.
Cut the resulting "cake" into square pieces. Pierce the canapes with skewers or toothpicks. Decorate the canapes with berries and sprinkle with powdered sugar.