Prepare the crust by combining graham cracker crumbs, 1/4 cup sugar, and melted butter in a mixing bowl. Grease a 9x13 inch baking pan and press the mixture into the bottom. Bake at 325°F for 10 minutes. Let cool.

Make the lemon curd layer by whisking together fresh lemon juice, lemon zest, 1 cup sugar, and eggs in a saucepan over medium heat. Stir continuously for 5-7 minutes until thickened. Remove from heat, add cubed butter, and strain to remove curdled bits. Let cool slightly.

Prepare the cream cheese layer by beating softened cream cheese, 1 cup sugar, and vanilla extract until smooth. Add eggs one at a time, mixing well after each addition, and fold in sour cream.

Pour the cream cheese mixture over the cooled lemon curd layer and swirl dollops of additional lemon curd on top. Bake at 325°F for 35-40 minutes until set.

Cool completely in the pan on a wire rack. Cover and chill in the refrigerator for at least 4 hours before serving. Slice into squares and garnish with fresh lemon slices or lemon zest.