Delightfully tart and sweet with a crunchy topping.
Preheat oven to 375⁰F.
Place rhubarb cubes in a large mixing bowl. Mix with flour and sugar.
Sprinkle lemon juice and zest over the mixture and stir to combine.
Place in a 9x13-inch baking dish.
Place butter cubes in a mixing bowl. Sprinkle with brown sugar and flour.
Using a pastry cutter, cut the butter into the flour and sugar, until the mixture is the size of peas. It will be necessary to scrape the butter off the pastry cutter several time. Alternatively, use a food processor to attain the same results.
Mix in the oats, walnuts, and cinnamon.
Evenly spread topping over the rhubarb. Leave it loose or press it down to form a crust
Bake for 55 to 60 minutes or until the crust is lightly browned
Serve it warm with ice cream, if desired.
Notes
Cover and refrigerate leftovers. Good cold or warmed in the microwave.