Wash and core Granny Smith apples. Cut apples into ½” thick rings, carefully slicing off the very top and bottom of each apple so every slice has flesh revealed.
Mix apple and lemon juice together with the cinnamon in a small bowl, set aside.
Melt butter or margarine in a large skillet over medium heat. Brown apple rings in butter in small batches, flipping after two minutes so that each side is nicely browned.
Remove each batch of apple rings from the skillet and add to a plate till all the apples have been cooked. Drop all apples back into the skillet and pour the apple and lemon juice mixture over them.
If using sugar, add it over the apples and then cover skillet, cooking for five more minutes over medium heat. Remove apple rings from skillet and plate. Enjoy alone, with other breakfast goodies or with whipped cream on top.