Put 1/2 cup passionfruit puree and 1/3 cup granulated sugar and blend until the sugar granules have dissolved. Add 2 eggs and blend on low speed until you have a bright-orange-yellow mixture. Transfer the contents of the blender to a medium pot or saucepan. Clean the blender canister.
Bloom the gelatin by sprinkling 1/2 teaspoon powdered gelatin evenly onto the surface of 2 tablespoons of cold water in a small cup. Make sure you sprinkle the gelatin evenly — pouring it into a pile on top of the water will not allow it to bloom properly since the granules in the center will remain hard. Allow the granules to soften entirely in the cold water for 3 to 5 minutes — the gelatin has bloomed when it has become soft. If it still has hard bits, it needs to bloom longer. If it's so soft it is falling apart, it's overbloomed; discard the gelatin and start over.
Heat the passionfruit mixture (from the first step) over low heat, whisking regularly. As it heats up, it will begin to thicken. Keep a close eye on it. Once it boils, remove it from the stove and transfer to the blender. Add the bloomed gelatin, 3/4 cup cold butter, and 1/2 teaspoon salt and blend until the mixture is thick, shiny, and super smooth. If you're using an immersion blender, divide the butter into 1 tablespoon portions and add the portions one by one, only adding the next portion when the previous one has been incorporated.
Once all the butter is incorporated, transfer the mixture to a heatproof container, and put in the fridge until the curd has cooled completely, at least 30 minutes. The curd can be refrigerated for up to 1 week; DO NOT FREEZE.