Arrange rhubarb evenly in bottom of a greased 1-quart casserole; sprinkle with cinnamon. Set aside.
Combine sugar and flour; cut in butter until mixture resembles coarse meal.
Sprinkle sugar mixture evenly over rhubarb.
Bake at 450 for 15 minutes. Reduce temperature to 375, and bake an additional 25 minutes or until lightly browned. Spoon into serving bowls while warm, and top with ice cream.
