01 - Preheat oven to 325°F. Line the bottom of a 9-inch springform pan with parchment paper, ensuring it sits flat against the base.
02 - Combine graham cracker crumbs, melted butter, and 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 set aside to cool completely.
03 - In a large mixing bowl, beat the softened cream cheese with an electric mixer 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 thoroughly after each addition. Blend in the sour cream, vanilla extract, flour, and lemon juice. Mix until just combined—avoid overmixing to prevent air bubbles.
05 - Pour the filling over the cooled crust and smooth the surface with a spatula. Bake for 45 minutes, or until the edges are set but the center still has a slight wobble when gently shaken.
06 - Turn off the oven and crack the door open. Let the cheesecake rest inside the cooling oven for 1 hour. This gradual cooling helps prevent cracks from forming on the surface.
07 - Remove the cheesecake from the oven and allow it to reach room temperature. Transfer to the refrigerator and chill for at least 4 hours, preferably overnight, until fully set.
08 - If using the topping, whisk together sour cream, powdered sugar, and vanilla extract until smooth. Spread evenly over the chilled cheesecake before slicing and serving.