Surprise Watermelon "Cake"

How does one come up with a cake at a very short notice? My mom and I bake a cake for my dad every year for his birthday. However, in 2015, he was supposed to be traveling on his special day. His work trip ended up getting cancelled at the last minute, meaning that we had to keep the tradition alive and get a cake ready in few hours. We quickly rushed to the store to get a watermelon and some whipping cream. My mom helped me cut the watermelon into a round cake shape, and I worked on whipping the cream and decorating the "cake" with some fresh fruit. Not only did it look beautiful, but it was also a somewhat healthy dessert! If I was to make this again, I would definitely whip the cream to be a bit more stiff since the cream was on the runnier side and started melting as we were setting the table. Nevertheless, the cake did not reveal itself before my dad cut it, so I think the purpose was served!