Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan.
In a bowl, combine the chopped dates with boiling water and stir in the baking soda. Let it sit for 10 minutes.
In another bowl, whisk together the flour, baking powder, and salt.
In a mixing bowl, cream the softened butter and brown sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
Gradually add the flour mixture to the butter mixture, alternating with the date mixture.
Fold in the chopped walnuts, if using.
Pour the batter into the prepared cake pan.
Bake for 30 minutes or until a toothpick inserted into the center comes out clean.