1. Wash the limes thoroughly, slice them in half, then cut into thin half-moon slices, removing any seeds.

2. Place the sliced limes in a large pot and cover with water. Soak for at least 4 hours or overnight.

3. After soaking, bring the limes and water to a boil. Lower the heat and simmer uncovered for 30-40 minutes until the peel is tender.

4. Measure the cooked lime mixture, then add an equal amount of sugar by volume. Stir well and bring to a boil over medium-high heat, stirring frequently.

5. Continue to boil the marmalade until it reaches the setting point (220°F or 104°C on a candy thermometer) or until it wrinkles on a chilled plate.

6. Ladle the marmalade into sterilized jars, leaving about ¼ inch of headspace. Seal the jars and process in a boiling water bath for 10 minutes for long-term storage.

7. Let the jars cool, then store in a cool, dark place or refrigerate for up to 4 weeks.