In a large bowl, whisk together the flour, baking powder, baking soda, salt, nutmeg, and cinnamon. Set aside.
In another bowl, cream together the sugar and butter until light and fluffy.
Beat in the egg yolks and vanilla extract until fully incorporated.
Add the dry ingredients alternately with the sour cream, starting and ending with the dry ingredients. Mix until just combined.
Cover the dough and chill it in the refrigerator for at least 30 minutes.
Lightly flour your work surface and roll the dough to about 1/2-inch thickness.
Cut out doughnuts using a doughnut cutter.
Heat vegetable oil in a deep fryer or large pot to 325°F (163°C).
Carefully fry the doughnuts a few at a time, about 2-3 minutes per side, or until golden brown.
Remove with a slotted spoon and drain on a cooling rack lined with paper towels.
Optionally, dust with powdered sugar or dip in a simple glaze once cooled slightly.
Enjoy warm for the best taste!
Serve these golden, tender Old Fashioned Doughnuts warm with a hot coffee — the perfect treat for a cozy morning or a sweet afternoon break!