Using a serrated knife, cut the cake layers evenly so they can be stacked.
Gel food coloring should be added to 1 cup of buttercream and mixed in until blended.
For the first layer, spread a thin layer of plain buttercream, add a circle of colored buttercream in the middle, and then add jam (if using).
Place the second layer on top and apply the first coat of icing using plain buttercream. Chill for 20 minutes.
Add the final coat and chill for another 10 minutes.
Before serving, make a concealed ring of colored buttercream in the middle of the cake. Then, warm the ganache and drip it around the edges.