Orange to wash, to remove finely (without the white part), peel, cut in half and squeeze the juice.
Cut the zest into thin strips, squeeze the juice out of half a lemon, prepare the remaining ingredients.
In a saucepan mix: orange juice and lemon, sugar, zest and half the necessary water. Bring to a boil, reduce and cook on medium heat for 5-7 minutes.
Starch dilute in the remaining water and stirring, pour into a saucepan, stir, remove from heat.