1-First Step: Preheat your oven to 350°F (175°C) and prepare a 9×9 inch baking pan by greasing it or lining with parchment paper.

2-Second Step: In a mixing bowl, combine the flour, sugar, baking powder, and salt to create the crust mixture, but use the exact Shortbread Crust ingredients provided for best results.

3-Third Step: Mix melted butter, sugar, vanilla, salt, and lemon zest, then stir in flour until combined. Reserve exactly ¾ cup of the mixture and chill it. Press the remaining crust into the pan and bake for 18 minutes.

4-Fourth Step: For the filling, beat cream cheese until smooth, add sugar and lemon zest, and beat again. Then mix in eggs, yogurt or sour cream, lemon juice, and salt. Stir in flour and gently fold in blueberries.

5-Fifth Step: Pour the filling over the pre-baked crust, scatter extra blueberries on top, and crumble the reserved crust over the filling. Optionally, sprinkle with coarse sugar for a nice crunch.

6-Sixth Step: Bake for 55 60 minutes until a toothpick inserted in the center comes out clean.

7-Seventh Step: Cool completely on a wire rack, then refrigerate for at least 1 hour. Lift the bars out using foil and slice into squares. Top with additional lemon zest if you like.