Instructions

• Preheat the oven to 375°F (190°C) and place a rack in the middle position. Line an 8-inch (20-cm) baking dish with heavy-duty aluminum foil so there is an overhang on at least two opposite sides; spray the foil lightly with nonstick cooking spray.
• Make the crust: In a medium bowl, stir together 1¼ cups graham cracker crumbs, 4 tablespoons melted unsalted butter, ¼ cup packed dark brown sugar, and 1/8 teaspoon salt until evenly combined and no lumps of brown sugar remain. Press the mixture firmly into the bottom of the prepared pan and about 1 inch (2.5 cm) up the sides. Bake the crust for 10 minutes, until set. Remove from the oven and set aside. Reduce the oven temperature to 325°F (165°C).
• Make the filling: In the bowl of an electric mixer fitted with the paddle attachment (or using beaters), beat 16 oz cream cheese, 1 cup granulated sugar, and 1½ tablespoons all-purpose flour on medium speed until just smooth, about 1 minute. Add ¼ cup sour cream, 3 large eggs, 2½ teaspoons vanilla extract, ½ teaspoon packed freshly grated lemon zest, 1 teaspoon lemon juice, and 1/8 teaspoon salt. Beat on low speed until just combined, about 1 minute, scraping the bowl and paddle once. Do not overmix.
• Assemble and bake: Pour the filling into the slightly cooled crust and smooth the top. Confirm the oven has reached 325°F (165°C), then bake for 40 to 45 minutes, until the filling is set at the edges but still a little jiggly in the center. An instant-read thermometer inserted about 1 inch (2.5 cm) in from the edge should read 180° to 190°F (82° to 88°C).
• Cool and chill: Remove the pan from the oven and let the cheesecake bars cool at room temperature for 30 minutes. Refrigerate until fully cold, at least 6 hours and preferably overnight.
• Serve: Use the foil overhang to lift the cheesecake out of the pan and place it on a cutting board. Cut into squares, wiping the knife clean with a damp cloth between slices. Keep the bars refrigerated until ready to serve.