Combine the flour, baking powder, and salt in a medium bowl.

Using a handheld mixer and a separate medium bowl or a stand mixer fitted with the paddle attachment, beat together the butter and sugar. Add the sour cream and beat until combined.

Add the flour mixture to the sour cream mixture and beat until just combined.

Wrap in plastic wrap and place in the fridge to chill for 20 minutes.

Preheat the oven to 375°F and line two baking sheets with parchment paper.

Unwrap the dough and divide into two equal pieces. (Use a food scale for precision if you have one.)

Roll each piece of dough into a rectangle around 8 by 14 inches.

Spread the date paste evenly across one dough rectangle and sprinkle with walnuts.

Working from the longer end, firmly roll up the dough (not loosely as you might for cinnamon rolls or babka). As you roll up the dough, create more of a square-​shaped log, not perfectly round. Repeat with the other piece of dough.

Place each roll on a prepared baking sheet.

Using a sharp knife, cut indentations spaced 1 inch apart (not cutting all the way through the cookies, just through the top). This step will make it easier after the rolls are baked to cut them into pieces.

Bake for 26 to 28 minutes, until slightly golden. You can rotate the baking sheets halfway through baking.

Remove from the oven and allow to cool slightly. Sprinkle all over with powdered sugar. Then, slice all the way through each slit to separate into cookies.