Start by cutting the passion fruit in half, from the stem to the bottom. You may need a bit of force to get through the skin, they can be a bit tough.
Be forewarned, the juice will start to ooze out. Separate the halves as quickly as possible to avoid this. Lay this with the cut side up as in the photo to retain all that juice inside.
Alternatively you can cut the top off and scoop it out with a teaspoon, as though it were a soft boiled egg.
Additional information:
Here in Brazil, they will use the empty shell of the fruit to place a candle in during religious festivals and parades.