Good for juices, cakes, leche flan etc.
Grate zest from the lemon or orange rinds by scraping the surface of the rind with a hand grater. You can also use a zester but it will take a long time as you need to basically zest the whole surface.
Squeeze juice from the lemon or orange. Mix juice, zest and sugar (at least a cup for 2 lemons or oranges) in a sauce pan. Boil until it froths the reduce heat and simmer until it thickens or becomes syrupy. Remove from heat, cool and transfer to a jar. Can be kept unrefrigerated.