Have all ingredients at room temperature, about 70°F.
Preheat the oven to 325°F.
Toast on a rimmed baking sheet until lightly browned, 8 to 10 minutes:
2/3 cup sliced almonds
Let cool. (Leave the oven on.)
Grease an 8-inch round cake pan liberally with:
2 tablespoons unsalted butter, softened
Line the bottom of the pan with a round of parchment paper and butter the parchment as well. Press the toasted nuts into the butter on the bottom and sides of the pan. Sprinkle evenly with:
1 tablespoon sugar
Crumble into a large bowl, or a stand mixer with the paddle attachment:
7 to 8 ounces Almond Paste, or Marzipan
Add and beat until soft and well blended:
6 tablespoons unsalted butter, softened
Gradually add and beat on high speed until light, 2 to 3 minutes:
1/2 cup sugar
Whisk together in a small bowl:
3 large eggs
1 tablespoon kirsch or brandy
1/4 teaspoon almond extract
Gradually beat the egg mixture into the butter-sugar mixture just until combined. Whisk together in another small bowl:
1/3 cup all-purpose flour
1/4 teaspoon baking powder
1/4 teaspoon salt
Add to the butter mixture and mix until just combined.
Scrape the batter into the prepared pan and bake until a toothpick inserted into the center comes out clean, 35 to 40 minutes.
Let cool in the pan on a rack for 10 minutes. Run a thin knife around the cake to loosen it from the pan, then invert the cake onto the rack. Peel off the parchment paper and cool completely.