Using a small sharp knife, make a shallow cut at the circumference of the rambutan, slicing through the skin but not the fruit itself. Remove the top half of the skin and pop the rambutan out of the bottom to reveal two rambutan shell "cups." Reserve the fruit for another use.
If using a whole pomegranate, fill the sink with water. Then quarter the pomegranate, place the quarters in the sink, and use your fingers to release the arils. Collect all of the arils and dry. This method protects you and your kitchen from messy pomegranate juice!
Fill empty rambutan cups with pomegranate arils and serve!