For the topping: Combine all the ingredients to form a crumbly mixture. Set aside. For the cake: Beat together all wet ingredients including citrus rind. In a separate bowl, stir together the remaining dry ingredients. Add wet to dry until just moistened. Prepare a 10 inch glass baking dish by coating with a thin layer of olive oil or any heat safe oil and pour one half of the batter in. Layer the fruit and cover with the remaining batter. Sprinkle the topping mixture evenly over the cake. Bake at 350 degrees for 45 to 50 minutes or until evenly browned and baked in the middle.