Heat the oven to 175 C / 350 F. In a mixing bowl, stir together the graham cracker crumbs, 30 g sugar, and cinnamon. Pour in the melted butter and mix until the crumbs look like wet sand.

Press the mixture firmly into the bottom and up the sides of a 23 cm / 9-inch pie dish. Bake for 8 to 10 minutes until fragrant and just set. Leave the oven on and let the crust cool slightly while you make the custard.

In a 2-quart / 1.9 L saucepan, whisk together the 100 g sugar, cornstarch, and salt. Whisk in the milk until no lumps remain.

Set the pan over medium heat and cook, whisking constantly, for 8 to 10 minutes until the mixture bubbles and coats the back of a spoon, about 180 F / 82 C.

Ladle about 1/2 cup of the hot mixture into the egg yolks, whisking fast so they don't scramble. Pour the yolk mixture back into the pan and cook 2 more minutes, whisking, until thick. Remove from the heat and stir in the butter and 2 tsp vanilla.

Pour the warm custard into the baked crust and spread it into an even layer.

In a clean bowl, beat the egg whites and cream of tartar with a hand mixer on medium speed until foamy. Add the 90 g sugar 1 tbsp at a time, beating until stiff, glossy peaks form. Beat in the 1/2 tsp vanilla.

Spread the meringue over the warm custard right to the edges of the crust, sealing it against the graham crust so it won't shrink. Swirl the top into peaks with the back of a spoon.

Bake at 175 C / 350 F for 10 to 12 minutes until the peaks are golden brown.

Cool the pie at room temperature for 1 hour, then chill uncovered in the fridge for at least 2 hours before slicing.