In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium speed until creamy, 3 to 4 minutes, stopping to scrape sides of bowl. With mixer running, add egg, beating to combine. Beat in vanilla.
In a medium bowl, whisk together flour and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until a smooth dough forms.
Between 2 sheets of parchment paper, roll dough to ¼-inch thickness. Remove top sheet of parchment. Using a 3¼-inch round cutter, cut dough, rerolling scraps as necessary. Spoon 2 teaspoons Burnt Lemon Curd Filling into center of each dough circle. Fold dough in from three sides, and pinch edges together to seal, leaving a small opening over filling. Place 2 inches apart on prepared pans. Refrigerate for 1 hour.
Preheat oven to 350°F (180°C).
Re-pinch corners of hamantaschen to ensure they’re well sealed; bake until bottoms and corners are golden, 20 to 25 minutes, rotating pans halfway through baking. Let cool completely.
Recipe by Bake from Scratch at https://bakefromscratch.com/burnt-lemon-curd-hamantaschen/