Preheat your oven to 350 degrees Fahrenheit. This step is crucial for ensuring that your cheesecake bars bake evenly and set properly.
Line a 9×13-inch baking pan with aluminum foil, allowing two of the sides to overlap. This will help you lift the cheesecake bars out easily later on. Spray the foil and any exposed pan with non-stick baking spray to prevent sticking.
In the body of a blender or food processor, combine graham crackers, granulated sugar, and salt. Pulse until the crackers have transformed into fine crumbs. This crumb mixture will create a buttery, flavorful crust.
Add in the melted butter and stir well to combine. Press this mixture down evenly into the prepared pan to form your crust layer. Bake in the preheated oven for 10 minutes. This helps the crust set, creating a solid base for your cheesecake.
While the crust is baking, in a large bowl using a handheld electric mixer (or in a stand mixer fitted with the paddle attachment), beat the cream cheese until completely smooth. Scrape down the sides of the bowl as needed; this should take about 3 minutes.
Add in granulated sugar, eggs, and egg yolks, and beat until the mixture is smooth and creamy; this should take about 2 minutes. Make sure to incorporate all the ingredients well!
Turn off the mixer and fold in lemon zest and lemon juice using a rubber spatula. Stir until combined, ensuring that the lemon flavors are evenly distributed throughout the mixture.
Next, quickly fold in flour, stirring just until combined. Be careful not to overmix; this will lead to a denser cheesecake.
Pour the cheesecake batter on top of the partially baked crust. Set aside to make your blackberry swirl.
In a small food processor or blender, puree the blackberries until completely smooth. Press the mixture through a fine mesh strainer, discarding seeds and pulp. Stir in the granulated sugar for the topping.
Spoon the blackberry mixture over the unbaked cheesecake layer in a few dollops. Use a skewer or a knife to gently swirl the blackberry mixture into the cheesecake batter, creating beautiful swirls.
Bake in the oven for 35 to 40 minutes, or until the cheesecake layer is set at the edges and only slightly wiggly in the center. Keep an eye on it to prevent overbaking.
Once baked, place the pan on a wire cooling rack and let it cool at room temperature until the pan is no longer hot. This step helps to avoid cracks in your cheesecake.
After cooling, place the cheesecake bars in the fridge until completely chilled, about 2 hours. This chill time is essential for the best texture.
When ready to serve, use the overlapped aluminum foil to lift the cheesecake out of the pan and onto a large cutting board. Cut into 16 bars and serve. Enjoy!
