In a medium bowl, whisk together melted butter, granulated sugar, egg yolk, vanilla extract, and almond extract until well combined. Fold in ground almonds, flour, and salt. Set aside.

In another medium bowl, whisk together all-purpose flour, baking powder, baking soda, and salt until well mixed.

In a large mixing bowl, beat softened butter with light brown sugar and granulated sugar until light and fluffy, about 2 minutes.

Add the mixture from the first bowl to creamed butter and sugars, beating on low until pale and fluffy.

Gradually add the dry mixture and remaining ground almonds to the wet mixture and mix until just combined.

Portion the dough into 18 balls on a lined baking sheet. Create an indent in each ball, fill with frangipane, and top with sliced almonds.

Preheat the oven to 350°F (175°C) and bake cookies for 12-13 minutes until golden brown.

Allow cookies to cool on a wire rack for about five minutes and dust with powdered sugar before serving.