In a small bowl, combine melted unsalted butter, granulated sugar, egg yolk, vanilla extract, and almond extract. Mix in ground almonds and all-purpose flour with a pinch of salt until smooth.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until well combined.

In a large mixing bowl, cream softened unsalted butter with brown and granulated sugars using an electric mixer until fluffy. Add the egg yolks and extracts, mixing until combined. Gradually incorporate the dry ingredients and ground almonds until just combined.

Using a large cookie scoop, portion the dough into balls and place them on a lined baking sheet. Create a small indentation in the center of each ball and fill with frangipane, topping with sliced almonds.

Preheat oven to 350°F (175°C). Bake cookies for 12-13.5 minutes until lightly golden. Use a circular cookie cutter to shape while warm if needed.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack. Dust with powdered sugar before serving.