Preheat oven to 375° F. Grease an 8-inch cake pan and line with parchment paper.
Sift together flour, soda, salt and spices. Beat butter and sugar until light and creamy, add eggs, beat well, then beat in molasses. Add boiling water and dry ingredients and beat until smooth.
Bake 30–40 minutes, until a toothpick comes out clean. Remove from oven and let let cool 10 minutes in the pan then turn out onto a rack to cool completely. The crumb will firm up the longer it sets, so try to wait until it’s cool to cut into it.