I use Rangpur Limes for this recipe but you can use a Tahitian Lime or other type of lime.
1 kg limes
2 litres (8 cups) water
1.7 kg caster sugar
Halve and juice the limes, reserving lime halves. Place the juice in a glass jar. Cover with plastic wrap or lid and store in the fridge. Trim the narrow end from each reserved lime half. Place in a large bowl. Cover with warm water. Soak for 6 hours or overnight to soften. Drain.
Cut each lime half into quarters and thinly slice into 2mm-thick strips. Place the lime strips, lime juice and cold water in a heavy-based saucepan. Bring to boil over medium-high heat. Reduce heat to low. Cover and simmer for 50 minutes to 1 hour or until rind is tender.
Add the sugar and cook, stirring, for five minutes or until the sugar dissolves. Increase heat to medium-high. Boil, stirring often, using a metal spoon to remove any scum that rises to the surface, for 45-55 minutes or until marmalade jells when tested. Spoon into sterilised jars. Store in a cool, dry place or the fridge once opened.
Testing for setting point
Chill a saucer in the freezer for 5 minutes. Spoon some marmalade onto the saucer and allow it to cool back in the freezer for 2 minutes. Push it with your finger and it should wrinkle. If it doesn't, continue cooking, testing every 5 minutes.
Wash and rinse the jars thoroughly. Leave them wet, with a tiny amount of water in each one. Heat them on high in the microwave oven for four minutes. They should be completely dry.