Pre-heat oven to 350F / 180C
Grease a springform cake pan or a normal round cake tin with butter
In a saucepan, simmer dates in water and vanilla until they are soft and almost mushy (about 3-4 mins)
Remove from heat and stir in baking soda. The mixture will foam a bit. Mix well and set aside to cool completely
In a bowl, cream butter with both sugars and orange zest until fluffy
Blend in eggs and then fold in flour, baking powder and salt
Then add the dates and mix until well combined
Then add the dates and mix until well combined
Pour into prepared cake pan
Bake for 40-50 mins or until a skewer inserted into the cake comes out clean. If the cake has crowned, cut off the top until the cake is level