Remove cream cheese, eggs, and sour cream from the fridge at least 1 hour before starting so they reach room temperature.
Preheat oven to 350°F (175°C). Butter a 9-inch square pan and line it with parchment paper, leaving an overhang on two sides.
Make the crust: in a food processor combine the vanilla wafer crumbs, shredded coconut, and a pinch of sea salt; pulse until very fine. Add the melted butter and pulse until evenly moistened.
Press the crumb mixture firmly into the bottom of the prepared pan. Bake 8–10 minutes until set, then remove and let cool completely on a wire rack. Reduce oven temperature to 325°F (165°C).
Make the cheesecake batter: in a food processor or stand mixer beat the room-temperature cream cheese, sour cream, 1/3 cup granulated sugar, and flour until smooth and lump-free.
Add the eggs one at a time, mixing well after each addition and scraping down the bowl as needed. Stir in the lemon juice, vanilla, and a pinch of salt until just combined.
Pour the batter over the cooled crust and spread into an even layer. Bake at 325°F (165°C) for 18–20 minutes, until the center is set but still slightly jiggly. Let cool to room temperature on a wire rack, then chill in the refrigerator at least 1 hour.
Prepare the passionfruit gelatin: sprinkle the powdered gelatin over 6 tablespoons cold water in a small bowl and let bloom for 5 minutes until no dry powder remains.
Meanwhile, heat the passionfruit juice (or strained pulp) with 1/4 cup sugar and 1/4 cup water in a small saucepan over medium heat, stirring until the sugar dissolves. Remove from heat.
Melt the bloomed gelatin briefly in the microwave (5-second bursts) until fully liquid, then whisk it into the warm passionfruit mixture. If you see any undissolved bits, strain through a fine mesh sieve.
Chill the passionfruit mixture in the refrigerator, stirring every 20–30 minutes, until it thickens but remains pourable—thick enough to suspend seeds without sinking.
Once the passionfruit layer is partially set, gently pour it over the chilled cheesecake using the back of a spoon or spatula to avoid disturbing the surface. Tap the pan to remove air bubbles and, if desired, scatter cleaned passionfruit seeds on top.
Refrigerate the bars at least 2 hours or ideally overnight until the passionfruit layer is completely set. Use the parchment overhang to lift the slab from the pan, transfer to a cutting board, and slice into squares (warm and wipe the knife between cuts for clean slices).