Steps
- Preheat the oven to 365°F / 185°C. Grease a 9 × 13in / 23 × 33cm glass baking dish.
- Mix 2¼ cups of all-purpose flour, 1½ teaspoons of baking soda, 1½ teaspoons of ground ginger, 1 teaspoon of cinnamon, ½ teaspoon of ground cloves, and ¼ teaspoon of nutmeg.
- Add the grated zest of 1 orange and 1 pinch of salt. Melt 1 cup of butter with 1 cup of molasses over low heat; cool.
- Beat 1 egg with 1 cup of sugar for 2 minutes, until pale. Beat in the flour mixture in batches, then the molasses mixture until smooth.
- Mix in ½ cup of boiling water and 3 tablespoons of sour cream. Stir in ¼ cup of dark rum and ¼ cup of chopped crystallized ginger.
- Pour into the dish. Bake for 50 minutes, until a skewer comes out clean.
- Turn off the oven and leave the cake inside with the door ajar for 10-15 minutes. Cool before cutting.