Preheat the oven to 200°C/400°F/Gas 6. Line a small cake tin (approx 16cm/6½in diameter) with baking parchment.
Toast the hazelnuts in a dry frying pan (skillet) over a low heat until they're golden brown. Chop them coarsely and discard as much of the skin as possible.
Melt the dairy-free spread in a pan. Remove from the heat, add the sugar and stir. Add the flour, aquafaba, cocoa powder, coffee and salt and stir to make a smooth batter.
Finally, stir in the hazelnuts, saving some to sprinkle on top of the cake if you wish.
Pour the batter into the prepared tin and top with the reserved nuts. Bake for about 18 minutes: the surface should be set but the cake should wobble in the middle if you shake it. Leave to cool completely and preferably leave in the fridge for at least a couple of hours before serving.