1 Rinse 2 screw-top jars (each 400 ml) (approximately 14 ounces) with boiling water and leave upside down to dry on a kitchen towel.
2 Halve melon, scoop out the seeds using a spoon, cut into quarters and peel.
3 Measure 500 g (approximately 2 1/4 cups) of the flesh and chop into small pieces.
4 Place the melon in a pot and stir in the jam sugar. Set aside for 20 minutes, covered.
5 Meanwhile, rinse limes under hot water and wipe dry. Finely grate the zest of 1 lime.
6 Juice both limes and add to the pot along with the zest.
7 Bring melon mixture in pot to a boil. Cook for 5-7 minutes over high heat, stirring constantly.
8 If needed, cook for another 1-2 minutes, or until the mixture has thickened.
9 Ladle hot jam into jars and seal immediately. Turn upside down on a damp cloth and then set upright again. Cool to room temperature, about 30 minutes. Refriegerate up to 3 weeks.