Prepare the Dough:

1. In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
2. Beat in the eggs one at a time, then add the vanilla extract.
3. In a separate bowl, whisk together the flour, baking powder, and salt.
4. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
5. Divide the dough in half, wrap in plastic wrap, and refrigerate for at least 30 minutes.

Prepare the Filling:

1. In a bowl, mix together the ground walnuts, granulated sugar, powdered sugar, cinnamon, and nutmeg.
2. Add the jam and mix until the filling reaches a spreadable consistency.

Assemble and Bake:

1. Preheat oven to 350°F (175°C).
2. On a lightly floured surface, roll out one half of the dough to a ¼-inch thickness.
3. Spread half of the nut filling evenly over the dough.
4. Carefully roll the dough into a tight log and slice into 1-inch pieces.
5. Place the slices on a parchment-lined baking sheet.
6. Repeat with the remaining dough and filling.
7. Bake for 12-15 minutes, until golden brown.
8. Cool on a wire rack before serving.