Cut the lemon in half.
Sprinkle the tablespoon of coarse kosher salt evenly over the surface of the cast iron skillet.
Use one half of the lemon to scrub the salted skillet surface, squeezing gently to release lemon juice as you scrub. Focus on areas with stuck-on food.
Continue scrubbing the skillet with the lemon and salt until all residue is removed.
Rinse the skillet thoroughly with warm water to remove all salt and lemon juice.
Dry the skillet completely with a clean, dry cloth or paper towels to prevent rusting.
Apply one teaspoon of vegetable oil or cast iron seasoning oil to the skillet surface using a paper towel, rubbing it evenly to maintain the seasoning.
Store the skillet in a dry place.