Stir finely chopped pieces into hot or cold dishes for a burst of salty, lemony flavor.
Bring a large saucepan of salted water to a boil; add lemons. Boil 5 minutes; drain. Run lemons under cold water until cool enough to handle.
Cut lemons into wedges; discard seeds. Toss lemon wedges with kosher sea salt, red pepper, and rosemary in a medium bowl. Pack into a 1-quart jar. Pour lemon juice over lemon wedges to cover. Seal jar, and chill at least 3 days or until rinds are soft and pliable. Shake container daily. Store lemons in refrigerator up to 1 year.