Preheat Oven: Preheat your oven to 350°F (175°C) and position a rack in the middle. Line the bottom of an 8-inch round cake pan with parchment paper and grease the pan.
Make the Batter: Crumble the almond paste into the bowl of a food processor. Add the granulated sugar and pulse until the almond paste is finely ground. Add the softened butter and process until smooth—it may form a ball, but keep processing until it becomes smooth. Add the eggs and almond extract, processing until well combined. Occasionally stop to scrape down the sides and bottom of the bowl. Sprinkle in the flour, baking powder, and salt, and process until the batter is fully blended.
Prepare to Bake: Pour the batter into the prepared cake pan, smoothing the top. Gently tap the pan on the counter to release any air bubbles. Top the cake batter with the sliced almonds and sprinkle 1-2 tablespoons of sugar over the almonds (layering half of the almonds and sugar first, then repeating with the remaining).
Bake: Bake the cake for 23-26 minutes, or until a toothpick inserted into the center comes out clean. Place the cake pan on a wire rack and cool for 30 minutes before carefully removing the cake from the pan. Return the cake to the rack to cool completely.
Serve: Serve the cake slightly warm or at room temperature. For an extra touch, dust with powdered sugar or top with whipped cream and fresh berries.