Follow these detailed steps to create your creamy lemon custard bars:

Step 1: Preheat the Oven
Preheat your oven to 350°F (175°C).

Step 2: Prepare the Crust
Mix Dry Ingredients: In a mixing bowl, combine the flour, sugar, and salt.
Add Butter: Cut the cold butter into small pieces and mix it into the dry ingredients using a pastry cutter or your fingers until the mixture resembles coarse crumbs.
Add Egg Yolk: Stir in the egg yolk until the mixture is evenly combined.
Press Into Pan: Line a 9×9-inch baking pan with parchment paper. Press the crust mixture firmly into the bottom of the pan to form an even layer.
Blind Bake: Bake the crust for 15 minutes, or until slightly golden. Remove from the oven and let cool.
Step 3: Make the Custard Filling
Beat Eggs and Sugar: In a mixing bowl, whisk together the eggs and granulated sugar until well blended.
Add Lemon Ingredients: Stir in the lemon juice, lemon zest, heavy cream, and flour until completely combined.
Pour Filling: Pour the custard mixture over the cooled crust.
Step 4: Bake
Bake for an additional 20-25 minutes, or until the custard is set and slightly wiggly in the center.

Step 5: Cool and Dust
Allow the bars to cool completely in the pan. Once cool, dust the top with powdered sugar, then slice into squares.

4. Variations of Lemon Custard Bars
Blueberry Lemon Custard Bars
Add 1 cup of fresh or frozen blueberries to the custard mixture before baking for a fruity twist.

Coconut Lemon Custard Bars
Stir in ½ cup of shredded coconut into the custard filling for a tropical flair.

Lavender Lemon Custard Bars
Add a teaspoon of culinary lavender for an aromatic touch.

Gluten-Free Version
Substitute all-purpose flour with almond flour for a gluten-free crust and custard.