Cut rhubarb into 1-inch pieces.
In slow-cooking pot, combine rhubarb with 3/4 cup sugar, cinnamon, cloves, and grated peel.
Cover and cook on low for 3 to 4 hours.
Remove cinnamon and cloves.
Spoon rhubarb into shallow baking dish.
In small bowl, mix together butter, flour and 1/3 cup sugar with fork or pastry blender.
Sprinkle over cooked rhubarb.
Bake in 400°F.oven for about 20 minutes.
Makes 5 to 6 servings.