Preheat oven to 325°F (160°C). Grease the bottom and sides of a 9-inch (23 cm) springform pan lightly and line the bottom with a circle of parchment paper for easy removal.

Combine 1.5 cups graham cracker crumbs, 2 tablespoons granulated sugar, and 1/4 teaspoon fine salt in a medium bowl. Pour in 6 tablespoons melted butter and stir until mixture resembles wet sand and holds together when pressed.

Press crumb mixture evenly into the bottom (and 1/2-inch up the sides if desired) of the prepared springform pan using the bottom of a measuring cup or a flat glass to compact it firmly and evenly.

Bake crust for 10 minutes, then remove from oven and set aside to cool while you make the filling. Keep oven on at 325°F (160°C).

Filling

Reduce the chance of lumps by ensuring 24 oz cream cheese is fully at room temperature. In a large mixing bowl or the bowl of a stand mixer fitted with the paddle, beat the cream cheese on medium speed until smooth and creamy, about 2–3 minutes, scraping the sides and bottom as needed.

Add 1 cup granulated sugar and beat on low-to-medium speed until incorporated, about 1–2 minutes. Scrape the bowl.

Add 1/2 cup sour cream and 2 teaspoons vanilla extract; beat briefly until combined.

Add 4 large eggs one at a time, mixing on low speed and stopping to scrape the bowl after each egg. Do not overmix; blend just until each egg is incorporated to avoid adding too much air.

Add 2 tablespoons all-purpose flour and 1 teaspoon lemon zest (optional); fold in with a rubber spatula or mix on low briefly until smooth. The batter should be silky and slightly thick.

Pour filling over the cooled crust in the springform pan and smooth the top with an offset spatula. Tap the pan gently on the counter a few times to release any large air bubbles.

Place the springform pan in a larger roasting pan. Carefully pour hot (not boiling) water into the roasting pan to reach about halfway up the outside of the springform pan to create a water bath (bain-marie). This helps prevent cracking and promotes even baking.

Bake in the preheated 325°F (160°C) oven for 50–65 minutes, or until the edges are set and the center still has a slight wobble (it will firm as it cools). Avoid overbaking; the ideal internal temperature is about 150–155°F (65–68°C) if using a thermometer.

Turn the oven off, crack the oven door open, and let the cheesecake cool in the oven for 1 hour to reduce the chance of top cracks.

Remove the springform pan from the water bath, run a thin knife around the edge to loosen (optional), and let the cake cool completely at room temperature on a wire rack for another hour.

Cover and refrigerate the cheesecake for at least 6 hours or preferably overnight to fully set and develop flavor.

Topping (optional)

If using the sour cream topping: whisk 1/2 cup sour cream with 2 tablespoons powdered sugar and 1/2 teaspoon vanilla extract until smooth.

Spread the topping evenly over the chilled cheesecake. Return to refrigerator for 15–30 minutes to set if desired.

Release the springform pan sides, transfer the cheesecake to a serving plate, and garnish with 1 cup fresh berries. Slice with a hot, dry knife (wipe the blade between slices) and serve chilled.