Pre-heat the oven to 180 degrees, gas 4. Grease three 15cm (6 in) sandwich tins then line the base of each tin with baking parchment.
Measure the butter, sugar, eggs, flour, baking powder and salted caramel extract into a large bowl and beat until thoroughly blended. Divide the mixture evenly between the tins and level out.
Bake in the pre-heated oven for about 20 minutes or until well risen and the tops of the sponge springs back when lightly pressed with a finger. Leave to cool in the tins for a few minutes then turn out, peel off the parchment and finish cooling on a wire rack.
Beat the butter until it is smooth and a pale yellow colour. Add in the Icing Sugar 1/3 at a time, making sure the sugar is fully incorporated after each addition and once all the sugar is added then add the salted caramel extracted then whisk again until its all fully incorporated.
Then put your buttercream in an icing bag and then add the icing to the bottom cake then put the next cake on top of the buttercream. Again, pipe buttercream on to the top of the second cake and place your third cake on top.
Spread icing all around the sides of the cake and add some to the top of the cake. Smooth the icing out to get rid of any excess and then decorate how you like.