Preheat oven to 350°F. Grease an 8x8-inch baking dish.
In a large bowl, toss together the rhubarb, 1 cup flour, granulated sugar, baking powder, and beaten egg.
4 cups chopped rhubarb, 1 cup flour, 1 cup granulated sugar, 1 teaspoon baking powder, 1 egg
Pour into the prepared baking dish.
Cut the butter into small cubes.
Place the brown sugar, ½ cup flour, salt, and cubed butter into the now-empty bowl. Use a fork, pastry blender, or your hands to cut the butter into the flour mixture until pea-sized lumps form.
½ cup unsalted butter, 1 cup brown sugar, ½ cup flour, ½ teaspoon salt
Pour the mixture over the rhubarb mixture in the pan.
Bake for 30–35 minutes, or until golden brown on top.
Serve warm with ice cream or whipped cream on top.
Notes
Want to jazz up this recipe? Add one of the following:
½ teaspoon cinnamon
⅛ teaspoon ground nutmeg
zest of one lemon
zest of one orange
Store any leftover crumble in the refrigerator for up to 5 days. I don't recommend freezing it, as the freeze/thaw process will leave you with very watery rhubarb at the bottom of the crumble.