Preheat oven to 375 degrees. Prepare 9 inch baking pan with waxed paper, or grease and flour. In a large bowl, whisk together dry ingredients in a bowl. Dissolve molasses in hot water in a separate bowl. In separate large bowl, beat together butter and sugar and then eggs, one at a time; and then add sour cream. Add dry ingredients in 4 parts, alternating with the mixture of hot water and molasses mixture, beating well to combine, and scraping bowl each time you add water or flour mixture. The batter will be runny. Pour into prepared pan and bake for about 40 to 45 minutes, or until a toothpick inserted in center comes out clean.