Preheat the oven to 180C (350F) and grease a springform cake tin with butter. Line the bottom with paper, grease and dust with flour. Shake out any excess.
Put the water, coffee and dates in a small saucepan and bring to the boil. Take off the heat, transfer to a food processor and pulse until smooth. Stir in the bicarbonate of soda – the mixture will froth up a little.
Beat the butter and sugar with a stand or hand mixer until pale. Add the eggs, one at a time, and whisk to combine. Scrape the bottom and sides of the bowl with a spatula as needed.
Sift in the flour, baking soda and salt and then add the date mixture. Fold everything together until batter is smooth.
Transfer the batter to the prepared cake tin and level. Bake for 50 minutes or until a skewer inserted in the centre comes out clean. Cool for 15 minutes before carefully removing from the tin.
Stir all the ingredients for the glaze in a small pan over low heat until smooth and glossy and pour over the cake letting it drip down the sides.