Heat the oil in a pot over medium heat, and add in the onion. Cook, until the onions are translucent, stirring continuously to ensure the pieces do not brown
Sprinkle the sugar, scotch bonnet lime zest, and lemon zest over the onions, and stir until the sugar dissolves. Pour in the lime juice, lemon juice, water and vinegar. Bring the ingredients to a boil. Add in the diced papaya, and adjust the seasonings with the salt, if desired.
Bring the mixture to a boil again, reduce the heat, and allow the mixture to simmer for 15 minutes. Take the pan off the heat, and let the mixture cool slightly. Carefully transfer the mixture to a blender, and puree the sauce until smooth.
Reserve some for Mahi-mahi - freeze the unused in individual portions in zip lock bags in the freezer!
For Mahi-Mahi Heat pan, add oil. Sear Fish and cook until done.