Summarize this article in one sentence.
Place the raspberries, sugar, and water in a small saucepan. Heat the ingredients over medium heat, whisking frequently, until the mixture thickens into a sauce. Remove from heat and set aside. Take the cake out of the refrigerator and place it on a serving plate. Remove the aluminum foil from the sides of the pan. Run a knife around the edge of the cake to loosen it from the sides, then unlatch the pan and unwrap it. If you have trouble removing the sides of the springform pan without breaking up the cake, try heating the knife in hot water before running it along the sides. Cut the cake into slices, then drizzle some raspberry topping over each one. Serve the cake with more raspberry topping on the side.
Make the raspberry topping. Remove the cake from the pan. Serve the cake.