1. Preheat oven to 175°C (350°F). Line the base and sides of an 8-inch springform pan with parchment and lightly grease.
2. Mix graham cracker crumbs, sugar, cinnamon, and salt. Stir in melted butter until mixture resembles wet sand.
3. Press firmly into the base and up the sides of the pan. Bake for 10 minutes, then cool.
4. Reduce oven to 150°C (305°F). Place a roasting pan on the bottom rack. Boil a pot of water.
5. Whisk eggs, yolk, lemon juice, and vanilla together. Set aside.
6. Beat cream cheese on low until smooth. Add sugar and cornstarch, mix until combined.
7. Slowly add the egg mixture in 3–4 additions on low speed.
8. Fold in sour cream gently with a spatula.
9. Pour into the crust, tap the pan to release air bubbles.
10. Pour boiling water into the roasting pan, place cheesecake on the middle rack above.
11. Bake for 1 hour 25–30 minutes, until edges are set and center jiggles slightly.
12. Turn off oven, crack the door, and leave cheesecake inside for 1 hour.
13. Chill uncovered in the fridge overnight.