Cream the softened butter in a large mixing bowl using a hand mixer or stand mixer until light and fluffy. Gradually add powdered sugar and mix until creamy, about 3-5 minutes.
Add vanilla extract (and optional citrus zest) to the creamed mixture and mix until evenly incorporated.
In a separate bowl, whisk together all-purpose flour, ground nuts, salt, and baking powder until well combined.
Gradually add the dry mixture to the butter-sugar mixture, mixing on low speed until the dough just comes together.
Preheat oven to 350°F (175°C). Shape the dough into round balls or crescent shapes, about 1 inch in size, and place them on a parchment-lined baking sheet.
Bake for 15-20 minutes, or until the edges are lightly golden. Keep an eye on them to avoid overbaking.
Allow cookies to cool slightly on the baking sheet before transferring them to a cooling rack. Dust with powdered sugar while warm.