Step 1: Preheat your oven to 350°F (175°C) and grease a 9-inch square or round baking pan. Place the chopped dates and baking soda in a heatproof bowl, pour the boiling water over them, and let them soak for 15 minutes.
Step 2: In a large mixing bowl, cream together the softened butter and brown sugar until light and fluffy. Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract and both the orange and lemon zest.
Step 3: Sift the flour, baking powder, ginger, cinnamon, and salt into a separate bowl. Gradually fold the dry ingredients into the butter mixture, followed by the soaked dates and their liquid, stirring until just combined.
Step 4: Pour the batter into the prepared pan and bake for 40-45 minutes, or until a skewer inserted into the center comes out clean. While the cake bakes, combine the sauce ingredients in a small saucepan over medium heat, simmering for 5 minutes until thickened.
Step 5: Poke several holes in the top of the warm cake and pour half of the citrus butterscotch sauce over it. Let it soak in for 10 minutes before serving with the remaining sauce on the side.