In a medium bowl, sift together the cake flour, baking powder, fine sea salt, ground nutmeg, and pumpkin pie spice. Set aside.

In a large mixing bowl, cream together the granulated sugar and unsalted butter until sandy crumbs form. Add egg yolks one at a time, blending fully before adding the next.

Gradually add the dry ingredients, alternating with sour cream and pumpkin puree, until the dough is sticky and fully combined.

Transfer the dough to a clean bowl, cover with plastic wrap, and refrigerate for at least 45 minutes.

For the glaze, whisk together the powdered sugar, light corn syrup, pumpkin pie spice, pumpkin puree, and vanilla extract on the side, adjusting with hot water for desired consistency.

Heat the canola oil in a pot to 325°F. Roll out the dough to 1/2 inch thickness and cut out shapes.

Fry the doughnuts in batches until golden brown, about 2-3 minutes per side, then place on a wire rack.

Dip each doughnut in the glaze and let the excess drip off before setting them back on the wire rack.