Preheat the oven to 350 degrees F. Grease 3 8-inch cake pans, and line the bottoms with circles of parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and brown sugar for a good 4-5 minutes, until light and fluffy.
Pour in the molasses and vanilla extract and mix on medium speed, scraping down the sides of the bowl as needed, until well combined. Add the eggs, one at a time, mixing well after each addition, and scraping down as needed.
In a medium bowl, whisk together the flour, baking powder, spices, and salt.
In a liquid measuring cup, combine the milk and water.
Add half of the dry ingredients to the butter and sugar mixture and mix on medium-low speed until just combined. Add the milk and water mixture, continuing to mix. Add the remaining flour mixture and mix just until no more flour is visible. Remove the bowl from the stand mixer and give it a good stir with a rubber spatula to make sure no flour remains on the bottom.
Divide the batter evenly between the cake pans. I used a scale for this, since the sides would be naked, and I really wanted to make sure the layers were of equal height. They will also bake more evenly this way. Rap the pans down on the counter to settle the batter.
Bake layers in the preheated oven for 22-27 minutes, until a toothpick inserted in the center comes out clean. Allow to cool in the pans for about 5 minutes. Run knife along the sides to make sure they will not stick and unmold the layers onto a cooling rack. Cool completely before frosting.