In a large bowl, stir together the ground beef, sloppy joe sauce, and french fried onions until well blended.
Spray the bottom of a 9x13 pan with cooking spray. Sprinkle half of the cheese on the bottom and top with the meat mixture, spreading to the sides. Top meat mixture with the remaining cheese.
In a medium bowl, combine the flour, milk, oil, eggs, and salt. Stir until well blended. Pour over the top of the sloppy joe mixture and cheese in the casserole dish.
Bake at 350 for about 30 minutes, or until the crust is set and very lightly browned.
