Pumpkin streusel bars

We had a wonderful pumpkin harvest this year, so I am always looking for new ways to use it. These cookies were a delicious discovery. The streusel topping makes them special: a soft center with a crisp crust.
Adjust servings in the full version
Pan size: 23*33 cm.
There is no need to grease the pan; the bars release easily.
First make the shortcrust base. Preheat the oven to 200°C.
Beat softened margarine with sugar and vanilla. Add sifted flour mixed with baking powder and sour cream.
Take the mold and spread the dough in a thin layer along the bottom. There is no need to make sides. Place the pan with the dough in the hot oven for 10-12 minutes.
While the base is baking, prepare the pumpkin filling. Mix flour with baking powder and salt in a separate bowl. Beat pumpkin puree with sugar and vanilla until smooth. Add flour and stir. It turns out to be a rather liquid mass. You can add chopped nuts if you wish. I didn't have it.
Remove the shortcrust base from the oven and let cool slightly. Reduce the oven temperature to 175°C.