Marmelad

Marmalade is a fruit preserve made from the juice and peel of citrus fruits boiled with sugar and water. The well-known version is made from bitter orange. It is also made from lemons, limes, grapefruits, mandarins, sweet oranges, bergamots, and other citrus fruits, or a combination. Citrus is the most typical choice of fruit for marmalade, though historically the term has often been used for non-citrus preserves. One popular citrus fruit used in marmalade production is the bitter orange, Citrus aurantium var. aurantium, prized for its high pectin content, which sets readily to the thick consistency expected of marmalade. The peel imparts a bitter taste.

Source: Wikipedia