Method

• 1.
  Slice the top and bottom off each orange and discard. Slice fruit into thin rounds, collecting the seeds in a muslin bag. Place orange rounds in a large bowl of cold water. Secure muslin bag and add to the water. Weigh down the fruit with a plate. Set aside to soak overnight.
• 2.
  Transfer fruit, soaking water and muslin bag to a large saucepan. Bring to the boil, then reduce heat to low and simmer for 30 minutes until rind is just tender.
• 3.
  Preheat oven to 140°C. Place the sugar on a baking tray in the oven for 5-6 minutes to dissolve gently. Add the sugar to the orange mixture and cook, stirring and skimming any surface scum, over same heat for 2-3 minutes. Add the lemon juice and bring to a rapid boil until it becomes a jelly-like consistency. (To test, place a spoonful of jam on a saucer and set aside in the fridge for 5 minutes - it should gel.) Remove the muslin bag and discard. Allow the jam to cool a little (the fruit will float to the top if the jam is too hot) before bottling in sterilised jars. Store for up to 3 months.