Preheat the oven to 425 degrees F (220 degrees C). Place butter in a 2-quart square glass baking dish and microwave on High until melted.
Whisk flour, sugar, baking powder, salt, and 1 teaspoon lemon zest together in a large bowl.
Whisk together 2 cups buttermilk, 1/2 cup lemon curd, and 1 tablespoon lemon juice in a bowl until smooth. Add to flour mixture. Stir just until combined.
Pour batter into the baking dish over the melted butter without stirring.
Dollop remaining 1/4 cup lemon curd evenly over the batter. Score the batter into 9 to 12 portions using a knife.
Bake in the preheated oven until biscuits are evenly browned and cooked through and the center registers 195 to 200 degrees F (90 to 93 degrees C) on an instant-read thermometer, 30 minutes. Cool for 5 minutes on a wire rack.
Whisk powdered sugar, 1 tablespoon buttermilk, 2 teaspoons lemon juice, and 1 teaspoon lemon zest together in a medium bowl until smooth. Pour glaze over warm biscuits and spread evenly.
