Step 1: Prepare the Graham Cracker Crust

1. Preheat the oven to 350°F (175°C).
2. Combine graham cracker crumbs, sugar, melted butter, and lemon zest in a bowl. Mix until crumbs are coated.
3. Press the mixture evenly into an 8×8-inch baking dish.
4. Bake for 10 minutes until set and slightly golden. Let it cool.

Step 2: Make the Lemon Blueberry Filling

1. In a large bowl, whisk together egg yolks and sweetened condensed milk.
2. Slowly add lemon juice and zest while whisking until the mixture thickens.
3. Fold in fresh blueberries gently.
4. Pour the mixture over the cooled crust and spread evenly.

Step 3: Bake and Chill

1. Bake for 15–17 minutes, or until the filling is set but slightly jiggly in the center.
2. Let cool to room temperature, then refrigerate for at least 1 hour.