Combine sugar, passion fruit, lemon juice, and salt. In a small saucepan on medium-low heat, melt the frozen passion fruit with the sugar, lemon juice, and salt until combined and the sugar dissolves - about 5 minutes.
Temper the eggs. In a small bowl, remove 1 tablespoon of the melted passion fruit mixture and vigorously whisk it into the egg yolks.
Combine egg yolks, passion fruit, and butter. Lower the stovetop to low heat. Whisking continuously, pour the tempered eggs and butter into the sauce pan with the remaining passion fruit mixture.
Whisk. Until the butter melts and the mixture is thickened (coats back of a spoon, it’ll thicken more as it sits) - about 8 minutes.
Strain. Pour the passion fruit curd through a fine mesh sieve (aka fine mesh strainer) into a bowl.
Store. Let it come to room temperature then transfer to a glass container and refrigerate until needed – up to 2 weeks.