Preheat the oven to 180C/160C Fan/Gas 4.
Grease and line two 20cm/8in sandwich tins.
Using a stick blender or small food processor blend together the cashew nut and milk to create a smooth, thick cream.
Using an electric hand whisk beat together the butter and sugar in a large mixing bowl until pale and fluffy.
Add the cashew mixture to the butter and sugar a little at a time, beating well.
Add the juice, grated zest of the orange and cinnamon to the mixture and beat again.
Now carefully mix in the flour a little at a time until you have a smooth, soft batter.
Divide the mixture between the two cake tins, place in the oven and bake for 30 minutes until risen and golden brown. (The cakes will spring back when gently pushed in the middle)
Leave to cool in the tins for about 5 minutes then turn out onto a wire rack to cool completely.
To make the butter icing place the butter, orange zest and icing sugar in a mixing bowl and whisk together, adding the orange juice a little a time to prevent it curdling (you may not need all the juice)
Sandwich the cooled cake together with the buttercream.