Prepare the crust

1. Crush the graham crackers into fine crumbs, then mix with melted butter and sugar until combined.
2. Press into a lined springform pan, smooth with a glass, and chill for 30 minutes.

Make the lemon cheesecake filling

1. Beat the cream cheese, sugar, and lemon zest until smooth and creamy.
2. Add sour cream, lemon juice, and vanilla, then mix until combined.
3. Add the eggs one at a time on low speed.
4. Sift in the cornstarch and fold gently.
5. For a perfectly smooth texture, pass the batter through a fine mesh sieve to remove any zest and air bubbles.

Bake the cheesecake

1. Pour the batter over the crust and place the pan in the oven with a water bath underneath.
2. Bake at 285°F (140°C) for 1 hour to 1h20 until slightly jiggly in the center.
3. Turn off the oven, let it cool slowly, then chill overnight.

Make the lemon curd

1. Whisk eggs, sugar, lemon juice, zest, and cornstarch until smooth.
2. Cook over low heat, whisking constantly until thickened.
3. Remove from heat and whisk in butter until smooth.
4. Strain and chill until fully cooled.

Make the Swiss meringue

1. Heat egg whites and sugar over a double boiler until warm.
2. Whisk on high speed until glossy and stiff peaks form.
3. Add vanilla and salt, then mix briefly.

Assemble and serve

1. Remove the cheesecake from the pan and spread the lemon curd on top.
2. Add the meringue, toast if desired, then slice and serve chilled.