Prep the pan and oven: Heat the oven to 325°F (165°C). Line the bottom of a 9-inch springform pan with parchment. Lightly spray the sides.
Make the crust: In a bowl, mix graham crumbs, cinnamon, a pinch of salt, and sweetener.
Stir in melted light butter until it feels like damp sand.
Press and pre-bake: Firmly press the mixture into the pan, going slightly up the sides. Bake for 8–10 minutes until fragrant. Cool for 10 minutes.
Soften the dairy: Ensure the light cream cheese is soft.
Cold cream cheese leads to lumps and overmixing later.
Blend the base: In a large bowl, beat cream cheese with sugar or sweetener until smooth, about 1–2 minutes. Scrape the bowl.
Add yogurt and flavor: Mix in Greek yogurt, vanilla extract, cinnamon, and a pinch of salt. If using, whisk in 1 tablespoon cornstarch or pudding mix.
Fold in protein: Whisk protein powder separately to break up clumps, then gently mix it into the batter until smooth.
Avoid overmixing to keep air out.
Add eggs last: Beat in eggs one at a time on low speed just until combined. Overbeating whips in air and can cause cracking.
Fill and smooth: Pour the batter into the cooled crust. Tap the pan lightly on the counter to release bubbles.
Bake low and slow: Bake at 325°F for 35–45 minutes.
The edges should be set and the center should still wobble slightly like Jell-O.
Cool gradually: Turn off the oven, crack the door, and let the cheesecake rest inside for 30 minutes. Then move to a rack to cool to room temp.
Chill to set: Cover and refrigerate at least 4 hours, preferably overnight. This firms the texture and mellows the flavor.
Add churro finish: Mix cinnamon and sugar/sweetener.
Lightly brush the top with a teaspoon of melted butter or a quick butter spray, then dust all over with the cinnamon-sugar blend.
Slice cleanly: Run a knife around the edge before unclasping the ring. Use a hot, wiped knife for neat slices.