Preheat your oven to 325°F and wrap the outside of a 9-inch springform pan with heavy-duty foil. This prevents water from seeping in during the water bath. Grease the inside lightly with butter.

Mix graham cracker crumbs, melted butter, and sugar until the mixture holds together when pressed. Press firmly into the bottom of your prepared pan. The crust should feel compact and even. Bake for 10 minutes until lightly golden.

Beat room temperature cream cheese until completely smooth and fluffy, about 3 minutes. Gradually add sugar, beating until well combined. Add eggs one at a time, mixing just until incorporated. Overmixing creates cracks, so stop as soon as each egg disappears into the batter.

Fold in sour cream, vanilla, and flour until just combined. The batter should be silky and smooth. Pour over the crust and gently tap the pan to release air bubbles.

Place the wrapped pan in a large roasting pan. Pour hot water halfway up the sides of the springform pan. This gentle heat prevents cracks and ensures even baking. Bake for 50-55 minutes until the center barely jiggles when shaken.

Remove from water bath and cool completely. Mix sour cream topping ingredients and spread over the cooled cheesecake. Refrigerate at least 4 hours or overnight before serving.