Buttercream with fondant accents. NOT sure what happened but this is the 2nd time a 2 tiered cake has SPLIT! Used wooden dowels and did a dowel all the way through the center. Couldn't find a box big enough so I put it in the same storage tote that I transported the other cake that split in. I'm thinking maybe the cakes are getting too hot in there. Anyway, I drove an hour to do what I could with the cake and ended up repairing the split well enough to make 2 cakes instead of the 1 tiered cake.