Line a 9x9 pan with parchment paper and preheat oven to 350°F.
In the bowl of a stand mixer with the paddle attachment, cream together butter and brown sugar for 3-4 minutes until fluffy.
Combine flour, baking powder, salt, and spices in a bowl.
Add the eggs one at a time to the butter mixture until fully incorporated. Then add molasses and vanilla. Combine.
Add the flour in parts alternating with the sour cream. Finish with flour mixture.
Pour the mixture into the pan and bake for 45 minutes or until a toothpick in the center comes out clean. Let it cool for about 15 minutes and then transfer it to a wire rack to cool completely.
Then sprinkle heavily with powdered sugar and serve with a cup of hot coffee!