Leave them in their tins until cool enough to handle, then carefully turn out onto wire racks to cool completely.While the cakes are cooling, make the filling. To make the vegan buttercream, whisk or beat together the dairy-free spread, icing sugar and remaining vanilla seeds until pale and fluffy. Dairy-free spreads do vary, so if the spread you are using is quite soft, try to avoid using electric beaters. Stir the ingredients together instead to avoid overworking it. However, if the mixture is too firm, use electric beaters to help lighten it and add 1-2 tbsp dairy-free milk when whisking.
