Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

In a stand mixer, beat the butter and sugar until light and fluffy, about 3-5 minutes. Add the egg and almond extract, mixing until just blended.

Gradually mix in the dry ingredients until just combined.

Scoop 1½ tablespoon-sized balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.

Bake for 8-11 minutes until the edges are set and the centers remain soft. Let cool for 10 minutes.

In a large bowl, beat the softened butter with the powdered sugar until creamy. Add almond extract and mix until smooth.

Once the cookies are cool, frost the tops generously with almond buttercream and optionally sprinkle with sliced almonds.