Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan, or line it with parchment paper.
Step 2: In a medium heatproof bowl, combine the chopped dates and baking soda. Pour the boiling water over the mixture. Stir gently and let it sit for 10-15 minutes.
Step 3: In a large mixing bowl, cream together the softened unsalted butter and granulated sugar until light, fluffy, and pale, about 3-4 minutes.
Step 4: Beat in the large eggs one at a time, ensuring each egg is fully incorporated before adding the next. Stir in the vanilla extract.
Step 5: In a separate bowl, whisk together the all-purpose flour, baking powder, salt, and ground cinnamon (if using).
Step 6: Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Gently fold in the softened dates (along with any remaining liquid) and the chopped nuts, if using.
Step 7: Pour the cake batter into your prepared 9-inch round cake pan, spreading it evenly. Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Step 8: Remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, carefully invert the cake onto a wire rack to cool completely. Slice and serve.