Line your 9-inch square baking pan with parchment paper, leaving some overhang on the sides for easy removal. This helps the bars come out cleanly after baking.
In a mixing bowl, combine the graham cracker crumbs with the melted butter and sugar. Stir until the mixture resembles wet sand and clumps together when pressed.
Press the crumb mixture firmly into the bottom of the prepared pan, spreading it evenly with the back of a spatula. Bake in a preheated oven at 175°C (350°F) for about 8 minutes until lightly golden. Let it cool slightly while you prepare the filling.
In a large bowl, beat the softened cream cheese with the superfine sugar using an electric mixer or whisk until smooth and creamy, about 2 minutes. This creates a luscious base for the filling.
Add the eggs one at a time, beating well after each addition, until fully incorporated and the mixture is smooth. The filling should be fluffy and slightly glossy.
Mix in the lemon juice, vanilla extract, and sour cream until just combined. The filling will become silky and slightly tangy, ready to be poured over the crust.
Pour the creamy filling over the cooled crust, spreading it evenly with a spatula. Give the pan a gentle tap on the counter to settle the filling and remove air bubbles.
Bake the bars in the oven at 175°C (350°F) for 25-30 minutes until the edges are lightly golden and the center jiggles slightly when gently shaken.
Remove the pan from the oven and let the bars cool on a wire rack for about 30 minutes. Then, transfer the pan to the fridge and chill for at least 4 hours or overnight to set completely.
Once chilled, lift the bars out of the pan using the parchment overhang. Slice into neat squares with a sharp knife, wiping the blade between cuts for clean edges.
Serve the cheesecake bars straight from the fridge for a firm, creamy bite. Enjoy the perfect balance of crunchy crust and velvety filling!
