Prepare the Passion Fruit Syrup: In a small bowl, combine passion fruit pulp, orange juice, and sugar (if using). Stir to combine and set aside.

1. Make the Mascarpone Filling: In a mixing bowl, beat the mascarpone cheese until smooth and creamy. Add powdered sugar and vanilla extract, and continue to beat until fully combined.
2. Whip the Cream: In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture.
3. Assemble the Tiramisu: Quickly dip each ladyfinger into the passion fruit syrup, then lay them in the bottom of a 9×9-inch dish. Spread half of the mascarpone mixture over the ladyfingers. Repeat with another layer of soaked ladyfingers, followed by the remaining mascarpone mixture.
4. Chill: Cover and refrigerate for at least 4 hours or overnight to allow flavors to meld.
5. Garnish and Serve: Dust with cocoa powder and garnish with fresh passion fruit pulp or zest before serving.