This sweet and tart Rhubarb Crisp has a filling made with fresh or frozen rhubarb covered generously with a simple oat crisp topping! It's an easy, delicious treat, especially when served warm with a scoop of vanilla ice cream!
Combine the rhubarb, sugar, cornstarch and lemon juice in an 8x8 or 9x9 baking dish. Toss to evenly distribute the sugar and cornstarch with the rhubarb.
In a large bowl, mix the butter into the oats, flour, cinnamon, and salt using a fork or your hands until it resembles pea-sized crumbs. Add chopped nuts, if using.
Sprinkle the crisp topping over the rhubarb filling, then bake for 35-40 minutes until the filling is bubbling and the crisp topping is lightly browned.
Cool for at least 15 minutes before serving with vanilla ice cream.
Notes
*If using frozen rhubarb, increase the cornstarch to 4 tablespoons.