Place the unopened can of evaporated milk in the refrigerator overnight. For extra volume when whipping, place it in the freezer for about 15 minutes before you start mixing. The milk must be very cold for it to whip properly.

Lightly grease a 9×13-inch baking dish with butter or nonstick spray. Line the bottom with parchment paper if you want very clean slices, though this is optional.

In a medium bowl, combine the graham cracker crumbs, 1/4 cup sugar, melted butter, and a pinch of fine sea salt. Stir until the mixture resembles damp sand and holds together when pressed between your fingers.

Pour the crumb mixture into the prepared pan. Use the bottom of a measuring cup or a flat glass to press it firmly into an even layer, especially around the edges. Chill the crust in the refrigerator while you prepare the filling.

In a small heat-safe bowl, add the lemon Jell-O powder. Pour in the boiling water and stir for 1–2 minutes, until completely dissolved. Set aside to cool to room temperature so it does not melt the whipped mixture later.

In a large mixing bowl, beat the softened cream cheese with 1 cup granulated sugar on medium speed until smooth and creamy, with no lumps. Add the lemon juice, lemon zest (if using), vanilla, and a pinch of salt. Beat again until the mixture is silky and well combined.

In a separate large, chilled bowl, pour in the very cold evaporated milk. Using a hand mixer or stand mixer fitted with the whisk attachment, beat on high speed for 3–5 minutes, or until very thick and fluffy, almost like whipped cream. It should at least double in volume.

With the mixer on low speed, slowly pour the cooled lemon Jell-O mixture into the cream cheese mixture. Beat just until combined, scraping down the sides of the bowl once or twice. The mixture will be somewhat loose at this stage.

Gently fold the whipped evaporated milk into the cream cheese–Jell-O mixture using a spatula. Fold rather than stir vigorously to keep the filling light and airy. Continue until no large streaks remain and the mixture looks pale and mousse-like.

Remove the chilled crust from the refrigerator. Pour the cheesecake filling over the crust and spread it into an even layer. Tap the pan gently on the counter a few times to release any large air bubbles.

If desired, sprinkle a handful of extra graham cracker crumbs evenly over the top of the filling for a traditional Woolworth-style look and a bit of extra crunch.

Cover the pan loosely with plastic wrap or foil. Refrigerate for at least 4 hours, preferably 6–8 hours or overnight, until the cheesecake is fully set and slices cleanly.

Use a sharp knife to cut the cheesecake into 12–16 squares, wiping the knife between cuts for neat edges. Garnish each piece with whipped cream and a thin lemon slice if desired, or serve plain.