Prep the pan. Line a 9x9-inch baking pan with parchment, leaving overhang on two sides for easy lifting.
Preheat oven to 325°F (165°C).
Make the crust. Crush the graham crackers into fine crumbs. Stir with brown sugar and a pinch of salt, then add melted butter. Mix until the crumbs look like wet sand.
Press and par-bake. Firmly press the crust into an even layer in the pan.
Use the bottom of a measuring cup to compact. Bake for 8–10 minutes, then let cool 5 minutes on the counter.
Soften the cream cheese. Ensure it’s truly soft. If needed, cut into chunks and let sit at room temp for 20 minutes.
This step prevents lumps.
Beat the filling base. In a mixing bowl, beat cream cheese on medium speed until silky and no lumps remain, about 1–2 minutes. Scrape the bowl.
Add sugar and cornstarch. Beat in granulated sugar and cornstarch until smooth. The cornstarch helps prevent cracks and gives clean slices.
Mix in sour cream, vanilla, lemon zest, and salt. Blend until just combined and velvety.
Add eggs last. Beat in eggs one at a time on low speed, stopping as soon as they’re incorporated.
Overmixing adds air, which can lead to cracks.
Pour and smooth. Spread the filling over the warm crust. Tap the pan gently to release air bubbles and smooth the top with an offset spatula.
Swirl the caramel. Warm caramel slightly if thick. Dollop spoonfuls over the surface and use a knife or skewer to gently swirl.
Don’t overdo it—distinct ribbons look best.
Bake low and slow. Bake at 325°F (165°C) for 28–35 minutes. The edges should be set, and the center should have a slight jiggle like gelatin.
Cool gradually. Turn off the oven, crack the door, and let the bars sit inside 10 minutes. Then transfer to a rack and cool to room temperature.
Chill to set. Cover and refrigerate at least 3 hours, preferably overnight.
This is key for clean slices and the best texture.
Finish and slice. Lift out using the parchment. If you like, drizzle extra caramel and sprinkle flaky sea salt. Use a hot, dry knife for sharp cuts, wiping between slices.