Supreming is a technique that removes the membrane from citrus fruit so it can be served in slices. To supreme an orange, lemon, lime, or grapefruit, begin by trimming off the very top and bottom of the fruit with a sharp knife. Next, set the fruit on end, and carefully cut the skin from its flesh, beginning at the top and following the curves down. Then, carefully cut out each section of the fruit by inserting the blade of the knife between the flesh and the membrane on both sides. The wedges should come out easily, leaving only the membrane intact.
Martha Stewart Living, Volume 8 June/July 1992