Zest and juice lemons; transfer 3 tablespoons (9 grams) zest and 6 tablespoons (90 grams) juice to a medium bowl. Whisk in ½ cup (100 grams) sugar, eggs, and salt until smooth; set aside.
Quarter juiced lemon halves, and thinly slice. Transfer to a medium saucepan, and cover with water. Bring to a boil over high heat; cook for 3 minutes. Drain, and pat dry with paper towels.
Return lemon slices to pan with remaining ¼ cup (50 grams) sugar; cook over medium-high heat, stirring constantly, until caramelized, 5 to 6 minutes. Remove from heat; let cool for 2 minutes. Stir caramelized lemons into lemon juice mixture. Pour mixture into pan; cook over medium-low heat until thickened, 2 to 3 minutes. Remove from heat; stir in butter. Let cool completely.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/burnt-lemon-curd-hamantaschen/