Preheat the oven to 350 degrees Fahrenheit and line a 9 x 13 pan with parchment paper leaving an overhang on the two long sides.
In a medium bowl, combine flour, baking powder, salt, and spices. Set aside.
In a stand mixer or in a large bowl and a hand mixer, cream together butter and brown sugar for about 4 minutes, until light and fluffy on medium/medium high speed.
Add the eggs, mixing well and scraping the sides of the bowl.
In a small bowl or pourable measuring cup, whisk together sour cream, milk and vanilla. Set aside.
Starting with the dry ingredients, add about ⅓ to the butter mixture and beat until combined.
Add half of the milk and mix well. Continue alternating dry and wet ingredients, ending with the dry ingredients. Stir only until the dry ingredients just disappear. Don’t overmix.
Pour the batter into the prepared pan and smooth the top. Bake for 30-35 minutes or until a toothpick inserted in the middle of the cake comes out clean.
Let cool in the pan on a wire rack.