So, you made some quark and now you are wondering what to do with it. Make some Rhubarb Streusel Cake, or for that matter, any Streusel cake. It is really easy to make and super delicious. Frankly, this is the only way I like my rhubarb. Now you might say “But aren’t there suppose to be strawberries in your rhubarb cake?” Nope, not this one. Don’t be afraid, it won’t be sour.