Preheat oven to 325ºF. Butter a 9″x3″ spring-form pan. Dust the pan with flour, shaking out the excess, and set aside. Sift together the cake flour, baking powder, and sugar into a small bowl. Set aside.
Place the almond paste and sugar in a medium-sized bowl. With your hands mix together the almond paste and sugar, breaking it up into small pieces. Set aside. In a stand mixer fitted with the whisk attachment, beat the butter until smooth. Add the almond paste mixture and beat until light and fluffy. Add the vanilla. One at a time, slowly add the eggs, scraping down the sides of the mixing bowl as necessary. Gradually add the flour mixture and mix until just combined. Pour the batter into the prepared cake pan and bake for 1 hour or until a knife inserted into the center comes out clean. Remove from the oven and let cool.
Move a knife carefully around the edge of the cake. Release spring-form pan and gently move the cake onto a serving dish. Once the cake has cooled, spread the jam on top. Top with toasted almonds and a dusting of powdered sugar.