COMBINE cream, parmesan and eggs in a large bowl. Combine flour, baking powder and salt; gradually stir into egg mixture. Set aside.
MELT butter in a large skillet over medium heat; add onion and cook, stirring often for 30-40 minutes or until onion is caramel colored. Remove onion from heat.
STIR onion into egg mixture; spoon into lightly greased 13x9-inch baking dish.
BAKE at 350° for 30 minutes or until set.