In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then add the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Divide the dough in half, wrap each half in plastic wrap, and refrigerate for at least 30 minutes.
In a bowl, combine the ground walnuts, granulated sugar, powdered sugar, cinnamon, and nutmeg.
Preheat oven to 350°F (175°C).
Roll out one half of the dough on a lightly floured surface to a 1/4-inch thickness.
Spread the nut filling evenly over the rolled-out dough.
Roll up the dough tightly in a jelly-roll style.
Cut the roll into 1-inch slices.
Place the slices on a baking sheet lined with parchment paper.
Bake for 12–15 minutes, or until the cookies are golden brown.
Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.