Preheat the oven to 180°C. Grease and line the base of a 7 cm deep, 22 cm (base) cake pan.
Place dates and baking soda into a bowl. Pour them into 1.5 cups of boiling water and allow them to stand for 20 minutes.
Using an electric mixer, beat butter, sugar and vanilla extract until pale and creamy. Add eggs, 1 at a time, beating well after each addition.
Add this mixture into the soaked dates mixture along with flour. Using a large metal spoon, fold through the date mixture and flour until well combined.