Preheat oven to 375�F. Spray an 8 inchx8 inch pan with non-stick cooking spray. Into prepared baking pan, place all filling ingredients. Toss until well mixed; set aside. To prepare tamale topping, in medium bowl, place flour, cornmeal, baking powder, baking soda, and salt; stir until evenly mixed. In a small bowl, beat yogurt, egg and margarine. Add to dry ingredients and stir just until dry ingredients are moistened. Spoon mixture evenly on top of vegatable filling. If desired, sprinkle evenly with chives. Bake 35-40 minutes, until filling is hot and bubbly, topping is lightly browned and a toothpick inserted in center of topping comes clean.