Preparation Steps

• Set a rack in the center of the oven and heat to 325°F. Line the base of a 9-inch springform pan with parchment, lock on the ring, and wrap the outside of the pan with two layers of wide heavy-duty foil (for a water bath). Put a kettle of water on to boil and place a large roasting pan on the oven rack.
• Make the crust: In a bowl, combine the graham cracker crumbs with the melted butter until the mixture looks like damp sand. Firmly press the crumbs into the bottom and 1 inch up the sides of the prepared pan. Bake for 12 minutes, then cool on a rack while you prepare the filling.
• Mix the filling: Using a stand mixer with the paddle or a hand mixer on low speed, beat the cream cheese until completely smooth, 1 to 2 minutes, scraping the bowl. Add the sugar and cornstarch and mix on low until velvety with no grainy spots. Blend in sour cream, heavy cream, vanilla, salt, and lemon zest just until incorporated.
• Add the eggs: Beat in the eggs and yolk one at a time on low speed, mixing just until each disappears. For an ultra-smooth texture, pass the batter through a fine-mesh sieve into a large pitcher or bowl.
• Bake in a water bath: Pour the batter into the cooled crust. Tap the pan a few times to release air bubbles. Set the springform in the roasting pan and pour in enough hot water to come halfway up the sides of the springform (avoid splashing). Bake at 325°F until the edges are set and the center wobbles like gelatin, 60 to 70 minutes.
• Cool gradually: Turn off the oven, crack the door open 1 to 2 inches, and let the cheesecake rest for 45 minutes. Remove the pan from the water bath, immediately run a thin knife around the inside edge to loosen, and cool on a rack until barely warm, 1 1/2 to 2 hours.
• Chill and serve: Refrigerate uncovered until cold, at least 8 hours or overnight. Remove the ring, peel off the parchment, and transfer to a platter. For clean slices, warm a thin knife under hot water, wipe dry between cuts, and serve.