Slice 1 orange in half. Remove any seeds from the halves, but keep the rinds on. Add both halves to a blender.
Juice the remaining oranges and discard the peels.
Add the orange juice and habanero to the blender (atop the two orange halves) and turn on high for a few minutes. Blend until you reach your desired consistency.
Place a pot over medium heat and add the mixture to it.
Squeeze in the juice from the lemon and add sugar to the pan. Stir gently to combine.
Boil slowly for 30-40 minutes or until the marmalade starts to darken in color.
Allow the marmalade to cool for 5 minutes before pouring into a sterile jar.
Video
Notes
Be careful not to allow the marmalade to stick to the bottom of the pan, as this will make the finished result more bitter.
When the preserve is almost ready, take a tablespoon of the mixture from the pan and place it onto a flat plate. Leave this in the fridge for five minutes and remove to see if it has set to a jelly-like consistency.