Preheat oven to 350° F and spray a pie dish with nonstick cooking spray. Make crust: In a food processor, pulse graham crackers until fine crumbs form. Transfer to a medium bowl, then add melted butter, sugar, and a pinch of salt and mix until combined.
Press graham cracker mixture firmly into prepared pie dish. Bake until crust is lightly golden, 8 to 10 minutes. Let cool to room temperature.
Make pie: In a medium bowl, whisk together milk and egg yolks until fully combined.
In a small saucepan, combine sugar, cornstarch, cinnamon, cayenne, and salt and whisk to combine. Add milk mixture and whisk again until no lumps remain. Bring mixture to a boil, then reduce heat and let simmer 1 minute.
