In a large bowl, whisk together eggs, egg yolks, pineapple juice, sugar, and cornstarch until the mixture is smooth and the cornstarch has dissolved.
Transfer the mixture to a medium saucepan. Cook over medium-low heat, stirring constantly with a wooden spoon, until the curd thickens—about 7-10 minutes. The curd is ready when it coats the back of the spoon and reaches the consistency of pudding.
Remove from heat and immediately stir in the butter pieces until fully incorporated.
Strain the curd through a fine-mesh sieve to remove any lumps or bits of scrambled egg, then transfer to a small bowl.
Cover the bowl with plastic wrap, ensuring the wrap directly touches the surface of the curd to prevent a skin from forming.
Refrigerate for at least 2 hours, or until set, before serving.