Step 1

Rinse limes; pat dry. Cut off ends and upend on a cut side. Make 2 perpendicular slits lengthwise into fruit to form an X, cutting only three-fourths of the way down. Pack lots of salt into slits and place limes into jar, pressing to compact and release juices. Seal jar; let limes sit at room temperature 12 hours. Uncover and press firmly again to compact. Repeat once or twice daily until limes are softened and submerged in juices, 2–3 days. (If there is not enough juice to submerge limes after 3 days, add fresh lime juice to cover.) Chill 1 month before using.

Step 2

Do Ahead: Limes can be preserved 6 months ahead. Keep chilled.