01 - Preheat the oven to 325°F (160°C). Line the bottom of a 9-inch springform pan with parchment paper and set aside.
02 - Combine the graham cracker crumbs, melted butter, and granulated sugar in a bowl, mixing until the texture resembles wet sand. Press the mixture firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then remove and let cool completely.
03 - Using an electric mixer, beat the softened cream cheese in a large bowl on medium speed until completely smooth and free of lumps. Gradually add the granulated sugar, continuing to mix until well incorporated.
04 - Add the eggs one at a time, beating well after each addition. Blend in the sour cream, vanilla extract, flour, and lemon juice. Mix until just combined—avoid overmixing to prevent cracks.
05 - Pour the filling over the cooled crust and smooth the surface with a spatula. Bake at 325°F for 45 minutes, or until the edges are set but the center retains a slight jiggle. Turn off the oven, crack the door open, and let the cheesecake rest inside for 1 hour.
06 - Remove the cheesecake from the oven and allow it to cool to room temperature. Transfer to the refrigerator and chill for at least 4 hours, preferably overnight, for the best set and flavor.
07 - For the optional topping, whisk together the sour cream, powdered sugar, and vanilla extract until smooth. Spread evenly over the chilled cheesecake before slicing and serving.