Place an oven rack in the middle of the oven. Preheat the oven to 325 degrees F. Butter a 10-inch cake pan or spring-form pan. In a mixer with a whip attachment, beat the butter until creamy. Gradually beat in the sugar until light and fluffy. Add the eggs, 1 at a time, beating well after each addition. Beat in the vanilla extract.
Sift the cake flour, salt, and baking powder together and use a rubber spatula to fold the dry ingredients into this butter mixture until a soft dough forms and no white streaks of flour remain. Spread half the batter evenly in the bottom of the prepared pan. Stir the almond extract into the cherry preserves. Spoon the cherry preserves over the batter, spreading it within 2 inches of the border.
Drop the remaining batter by large spoonfuls or pipe it with a plain tip over the preserves. Spread the batter carefully over the jam to the edge of the pan. Sprinkle with sliced almonds, if using.
Bake for 40 to 50 minutes, or until a bamboo skewer inserted into the cake comes out with a few moist crumbs clinging to it. Let cool in the pan on a wire rack. Unmold the cake and dust with confectioners' sugar.