Rhubarb citrus coffee cake

1. Preheat oven to 350 degrees. Butter 8 inch pan. 2. Combine flour, baking powder, salt and orange zest in a bowl. 3. Beat together 3/4 cup sugar and butter until well combined , for 5 minutes. Stir in oj and egg until well mixed. Mix may look curdled. 4. Stir in flour mix into oj mix just until flour mixture is evenly moistened. Fold in rhubarb. Pour batter into prepared pan. 5. Prepare the topping: combine sugar and cinnamon. Sprinkle topping over batter. 6. Bake the cake for 30 minutes or until pick comes out clean. Serve coffee cake warm.