Microwave the red pepper flakes in the olive oil for about 30 seconds. Place the spinach on the bottom of the baking pan. Place the filets on top of that. Cut the asparagus in half and place these and the onion on top of the filets. Squeeze the lime juice on top and then pour olive oil over top as well. Bake at 450 degrees with an aluminum foil tent, for 10-12 minutes or until fish is done.