Step 1: Prepare the Pan and Preheat the Oven
Start by preheating your oven to 350°F (175°C). While the oven heats up, line a 9×9 inch baking pan with parchment paper. The parchment paper will help you easily lift the bars out of the pan once they’ve cooled, making cutting and serving a breeze. If you don’t have parchment paper, you can lightly grease the pan, but parchment paper ensures the bars won’t stick.

Step 2: Make the Crust
In a large bowl, combine the all-purpose flour, granulated sugar, light brown sugar, salt, and baking powder. Mix the dry ingredients together until they’re well combined. Next, pour in the melted butter and stir until the mixture becomes crumbly. The texture should resemble coarse crumbs, and it should hold together when pressed. This is your crust mixture, which will form both the base and topping of the bars.

Step 3: Press the Crust into the Pan
Take about two-thirds of the crumbly mixture and press it firmly into the prepared pan. Use the back of a spoon or your fingers to press it into an even layer that covers the bottom of the pan. Make sure to press it down well so that the crust holds together during baking. Place the pan in the oven and bake the crust for 15 minutes, or until it’s lightly golden. This initial baking step will help set the crust, providing a sturdy base for the creamy lemon filling.

Step 4: Make the Lemon Filling
While the crust is baking, it’s time to prepare the lemon filling. In a large bowl, whisk together the sweetened condensed milk, egg yolks, heavy cream, and salt. The sweetened condensed milk adds richness and sweetness, while the egg yolks provide the necessary structure and texture. Once the mixture is smooth, gradually whisk in the fresh lemon juice. The lemon juice will provide the tangy flavor that defines this dessert, giving it a refreshing and zesty taste. Make sure the lemon juice is fully incorporated into the filling mixture, and whisk until the filling is smooth and creamy.

Step 5: Assemble the Bars
When the crust has finished baking, remove the pan from the oven. Pour the lemon filling over the hot crust, spreading it out evenly with a spatula. Once the filling is in place, sprinkle the remaining one-third of the crumb mixture over the top. Don’t worry if it doesn’t cover the entire surface—this will create a lovely crumbly topping when the bars bake.

Step 6: Bake the Bars
Place the pan back in the oven and bake the bars for an additional 15-20 minutes. The top should be golden and slightly set, and the filling should be firm around the edges but still a little jiggly in the center. The lemon filling will continue to set as the bars cool, so don’t worry if it’s not completely firm right out of the oven.

Step 7: Cool and Refrigerate
Once the bars are done baking, remove them from the oven and allow them to cool completely in the pan. The cooling process is important because it helps the filling firm up, making it easier to cut the bars without them falling apart. After the bars have cooled, refrigerate them for at least 4 hours, or up to overnight, to allow the flavors to meld and the filling to fully set. This chilling step ensures that the bars hold their shape and provides the refreshing, cool texture that makes them so irresistible.

Step 8: Slice and Serve
Once the bars have chilled and set, remove them from the fridge and use the parchment paper to lift them out of the pan. Place the bars on a cutting board and slice them into squares. Serve chilled, and enjoy the perfect balance of tart lemon and sweet, crumbly goodness. These bars are a delightful treat for any occasion, from summer picnics to holiday gatherings.