Preheat oven to 350ºF. Line a 9×13-inch baking dish with aluminum foil. Lightly spray with cooking spray.: The warm, yeasty smell of the oven coming up to 350ºF signals the start of transformation, and lining the pan with foil creates an easy lift out later. Properly prepping the pan prevents sticking and ensures clean edges when you cut bars. A common mistake is skipping the spray, which can make removal messy; take the extra minute to prepare the dish, and you will be rewarded with tidy squares.
Press one can of crescent rolls in the bottom of the prepared baking dish. Bake in the preheated oven for 7 minutes.: As the dough warms, you will notice a buttery aroma and the dough beginning to set, edges slightly puffed. This brief bake firms the bottom layer so it holds the filling without becoming soggy. If you underbake here, the crust can stay doughy after the final bake; if you overbake, it may become too crisp. Seven minutes gives a tender, sturdy base.
In a medium bowl, combine lemon juice, zest of 1 1/2 lemons, cream cheese, 1/2 cup sugar, and vanilla extract. Beat together with an electric hand mixer until smooth.: The mixing produces a glossy, airy filling that smells of citrus and sweet cream. As you beat, scrape the bowl to eliminate streaks and achieve a homogeneous texture. If the cream cheese is not fully softened, you may get small lumps, so room temperature cheese is key for a perfectly smooth result.
Spread cream cheese mixture over partially baked crescent roll crust.: The contrast is immediate, the pale, velvety filling settling into the golden shell. Use a spatula to smooth it level, ensuring even thickness so each bar bakes uniformly. If you pile it too high in one area, that section may take longer to set, so aim for an even layer for consistent texture across the pan.
Unroll the second can of crescent roll dough and layer over the cream cheese mixture, gently stretching dough to the edges.: When you place the top layer, you will see the filling peek out slightly at the seams, promising a creamy center. Stretching gently helps the dough meet the pan edges without tearing. Avoid pulling aggressively, which can create thin spots that brown too quickly. Take your time to ease it into place so it seals well.
Brush the dough with melted butter.: The melted butter adds sheen and promotes even browning; when brushed, the surface takes on a glossy finish that turns golden in the oven. This step also helps the sugar adhere, creating those little crunchy highlights when baked. Brush sparingly and evenly, because excess butter can pool and make the top greasy.
In a small bowl, combine 3 tablespoons of sugar and the remaining lemon zest. Sprinkle sugar mixture over the melted butter.: The fragrant sugar releases a burst of citrus oil with each sprinkle, and as it bakes it develops tiny crunchy crystals. This topping gives the bars a lively finish, both visually and texturally. Be mindful to distribute the mixture evenly, so it caramelizes uniformly and does not burn in isolated spots.
Bake for 30 minutes, until golden brown.: As the pan roasts, the kitchen fills with warm, buttery, citrus notes, and the top will turn an even golden color. Look for a lightly browned surface, bubbling edges, and a set filling that no longer jiggles in the center. Overbaking can dry the filling, while underbaking leaves it too soft, so check toward the end and rely on color and a gentle jiggle test.
Cool the bars for 20 minutes and then refrigerate for an hour.: Cooling lets the filling firm and settle, so when you chill them the texture becomes dense and sliceable. The cooling phase also deepens the flavors as the lemon melds with the cream cheese . Cutting too soon can cause the filling to smear, so patience at this stage ensures tidy, pleasing bars.
Lift the dessert from the baking dish and transfer to a cutting board. Cut the dessert into bars and enjoy.: Lifting the foil should reveal clean edges, and as you slice you will hear a slight, satisfying give as the knife passes through the tender crust and creamy middle. For neat squares, use a sharp knife and wipe it between cuts. A dull knife or sawing motion can cause uneven edges, so take a steady, single stroke for the best presentation.