In a large bowl combine flour, baking powder, poppy seeds and salt. Set aside.
Using a stand mixer or hand blender blend sugar and butter until light and fluffy. Add in eggs and continue mixing until fully combined, scraping down the sides as needed. Add in almond paste and extract and blend until smooth. Once smooth add in buttermilk and blend until fully incorporated.
With the mixer on low speed add in flour mixture and stir until smooth.
Pour finished batter into a well greased bundt pan and place on the center rack. Bake cake for 50-60 minutes or until cooked through.
While the cake is baking whisk together powdered sugar, milk and almond extract
Allow cake to cool completely before removing from pan. Top with glaze and slivered almonds and enjoy!