1Preheat oven to 350°F. Place melted butter in 13 x 9-inch baking dish; set aside.
2In large bowl, beat eggs, stir in milk. Stir in flour and baking powder until well blended. Stir in cheese, spinach and onion. Spoon egg mixture into baking dish.
3Bake 35 minutes or until center is set. Cool 30 minutes; cut into 6 rows by 4 rows. Serve immediately.