Cake:

• Preheat oven to 350°F with a rack in the middle of the oven. Line the bottom of an 8-inch round cake pan with parchment paper and grease the pan.
• Crumble almond paste into food processor bowl. Add granulated sugar and pulse until almond paste is finely ground. Add butter and process until smooth (it will turn into a ball; just keep processing until it smooths out). Add eggs and almond extract and process until combined, occasionally stopping the processor and scraping sides and bottom of bowl. Sprinkle in flour, baking powder, and salt, and process until blended. 
  
• Pour batter into prepared pan and smooth the top. Tap the pan on the countertop a few times to remove air bubbles. Top the cake batter with sliced almonds and 1-2 tablespoons sugar (I like to add half the almonds, sprinkle over half the sugar, then repeat with remaining almonds and sugar).
• Bake for 23-26 minutes, until a toothpick inserted into the center comes out clean. Place the pan on a wire rack. Cool for 30 minutes, then carefully remove it from the pan and place the cake back on the rack to cool. If a few almonds fall off the top you can just press them back on. If desired, you can dust the cake with powdered sugar or serve with the berry topping mentioned below.