For the optional garnish, cut a slice of lime and then cut a slit from the center to the edge of the slice. Twist it into a spiral and use a cocktail pick to pin it in place. Set it aside.
Start making the drink by adding the lime juice, passion fruit syrup, pineapple juice, Limoncello, and rum(s) to a cocktail shaker.
Fill the shaker with ice and shake well, about 15-20 hard shakes.