Preheat your oven to 325°F (163°C) and grease the inside of your 9-inch springform pan with butter or non-stick spray. If using a water bath, wrap the outside of the pan tightly with two layers of heavy-duty aluminum foil.
Combine graham cracker crumbs, 1/4 cup sugar, and melted butter in a bowl, stirring until the mixture resembles wet sand. Press firmly and evenly into the bottom and 1 inch up the sides of the prepared pan, then bake for 10 minutes until lightly golden. Let cool completely.
Beat the softened cream cheese on medium speed for 3–4 minutes, scraping down the bowl frequently, until completely smooth and lump-free. Add the sugar and flour and beat for another 2 minutes until fully incorporated.
Add the sour cream, fresh lemon juice, lemon zest, and vanilla extract to the cream cheese mixture and mix on low-medium speed just until combined, scraping the bowl as needed. Do not overmix at this stage.
Add the eggs one at a time on low speed, mixing only until each yolk disappears into the batter (about 15–20 seconds per egg). Stop the mixer as soon as the batter is uniform — overbeating adds air that causes cracking.
Pour the filling over the cooled crust and use an offset spatula to spread it into an even, smooth layer. Tap the pan gently on the counter 3–4 times to release any trapped air bubbles.
Bake at 325°F for 55–65 minutes, until the edges are set but the center 2–3 inches still has a slight jiggle like gelatin. Do not open the oven door during the first 45 minutes of baking.
Turn off the oven and leave the cheesecake inside with the door cracked open for 1 full hour. Once removed, immediately run a thin knife around the edge of the cheesecake, then cool completely on a wire rack for 1–2 hours.
Cover the cooled cheesecake loosely with plastic wrap and refrigerate for a minimum of 6 hours, or overnight for best texture and flavor. Do not skip this step.
Remove the springform pan sides, then beat the cold heavy cream, powdered sugar, and lemon zest to soft peaks and spread or pipe onto the cheesecake. Garnish with lemon slices, lemon curd, or mint leaves and slice with a hot, dry knife for clean cuts.