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

In a large bowl, beat the softened butter with 1 cup granulated sugar until light and fluffy, about 2–3 minutes.

Add the eggs one at a time, beating well after each addition, and stir in the vanilla.

In a separate bowl, whisk together 3 cups flour, baking powder, and salt.

Gradually mix the dry ingredients into the wet ingredients until just combined. Do not overwork the dough.

Divide the dough in half, shape each half into a disc or short log, wrap tightly in plastic, and refrigerate for at least 30 minutes.

In a bowl, combine ground walnuts, 1/3 cup granulated sugar, powdered sugar, cinnamon, and nutmeg.

Stir in jam a spoonful at a time until the mixture is spreadable but not runny.

On a lightly floured surface, roll one chilled dough half into a rectangle roughly 9x12 inches and about 1/4-inch thick.

Spread half of the nut filling evenly over the dough, leaving a 1/4-inch border around the edges.

Roll the dough tightly from the long edge into a log. Pinch the seam to seal.

Slice the log into 1-inch pieces and place them cut-side down on the prepared baking sheet. Repeat with the second dough half.

Bake for 12–15 minutes, until the edges are just turning golden.

Transfer cookies to a wire rack to cool completely before serving.