Grease a 9-inch or 10-inch round baking pan. Preheat the oven to 350°F.
In a small bowl, add one cup of the pitted dates and add one teaspoon of the baking soda. Cover with boiling water and set aside and let the dates soak for 10 to 15 minutes until they've softened.
Use a blender or food processor to blend the softened dates and the water they were soaked in to form a paste. Set aside.
In a large mixing bowl, use a stand mixer or electric hand whisk to cream the softened butter and granulated sugar until it is smooth and pale yellow, after about 3 to 5 minutes.
Add the eggs and vanilla and mix again until it is smooth, after about 2 to 3 minutes. Set aside.
In a separate large mixing bowl, whisk together the flour, salt, baking powder and the remaining ½ teaspoon of baking soda.
Add the wet ingredients and the blended dates into the dry ingredients and mix just until you no longer see pockets of dry flour.
Fold in the chopped walnuts and remaining ½ cup dates, roughly chopped. Pour the batter into your prepared baking dish.
Bake for 35 to 40 minutes, until a toothpick inserted into the center of the cake comes out clean.