Place plastic wrap in a large, deep dish. Add half the salt and sugar mixture to the bottom of the dish. Add the salmon steak. Cover salmon with remaining salt and sugar mixture.
Close the plastic wrap tightly over the salmon. Cover with another piece of plastic wrap. Add a dish or plate on top and place something heavy in it (like canes). Place in the refrigerator for 24 to 36 hours.
After 24 to 36 hours in the refrigerator, remove the salmon from the plastic wrap and rinse with cold water. Pat dry.