Trim the sides, bottom and top of each cake then split the cakes in 1/2 horizontally so you have 4 layers.

Flip the cakes so that the flat side of one cake is facing the bottom and the flat side of the other cake is on top,

Divide the buttercream in 1/2, reserve one 1/2 for icing the cake, use the remaining for filling

Place the bottom layer on your cardboard cake circle or serving platter. Brush the layer generously with rum syrup,

Place 1/3 of the filling buttercream on the layer and spread it evenly to the edges. Repeat with the next three layers.

Ice the sides and top of the cake with the reserved buttercream.

Serve at room temperature