Wash and dry shad with paper towels. Notch both sides and sprinkle inside and out with salt. Place shad on large piece of heavy duty aluminum foil that has been sprayed well with Pam. Place bacon slices in notches and thick slices of onion on top of fish. Seal fish in the aluminum foil and place in a brown paper bag, (tuck open end under). Place on a cookie sheet that has been sprayed with Pam. Bake at 250 degrees for 6 or 7 hours.