Rhubarb Crumble Cake Bars are a tray bake version of a classic British dessert. This moist cake is topped with roasted rhubarb and scattered with a tasty crumble layer. What is rhubarb? Rhubarb is a leafy green plant with pink stalks popular in the UK. The leaves are inedible as they are poisonous so only the stalks are used. Technically rhubarb is a vegetable but it is largely considered ... continue reading...