A filling of cherries and kirsch-flavored whipped cream is standard in this classic German cake. To poach the cherries, in a small saucepan over medium heat, bring 1 3/4 cups water and 1/3 cup granulated sugar to a boil, stirring occasionally. Add 1 cup fresh pitted Bing or other dark sweet cherries, reduce the heat to low and cook until soft, about 10 minutes. Let the cherries cool, then drain; discard the syrup. Frozen or jarred cherries may also be used. Cook the frozen cherries as directed above. Jarred cherries have already been poached.