Preheat the oven to 350°F. Grease and flour a 9x13-inch baking pan.
In a large mixing bowl using a hand mixer (or in the bowl of a stand mixer), cream the butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Mix in the vanilla extract and molasses until smooth.
Scrape down the sides and bottom of the bowl to make sure everything is well combined.
In a separate bowl, whisk together the flour, salt, and spices. Add to the wet ingredients and mix just until incorporated.
Stir the baking soda into the boiling water (it will foam), then gently mix it into the batter. The batter will be very thin—that’s normal.
Pour the batter into the prepared pan and spread it evenly.
Bake for 35 to 45 minutes, or until the edges pull away from the pan and a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Let the cake cool slightly before serving. Enjoy warm or at room temperature, with whipped cream, a dusting of powdered sugar, plain, or try my cream cheese frosting for a bakery style cake (see Notes).