Prep your pan. Line the bottom of a 9-inch springform pan with parchment and lightly grease the sides. Preheat the oven to 325°F (163°C).
Make the crust. In a bowl, mix crumbs, sweetener, melted butter, and a pinch of salt until it resembles wet sand. Press firmly into the pan, going slightly up the sides.
Bake for 8–10 minutes, then cool while you make the filling.
Beat the cream cheese. In a large bowl, beat cream cheese until smooth, about 1 minute. Scrape the bowl so there are no lumps.
Add yogurt and sweetener. Mix in Greek yogurt, sweetener, vanilla, cornstarch, and salt. Blend until silky.
Incorporate protein powder. Sprinkle protein powder over the mixture and blend on low.
Avoid overmixing. You want a smooth, thick batter.
Add eggs last. Beat in eggs one at a time on low speed just until combined. Overmixing adds air and can cause cracks.
Fill and smooth. Pour the batter over the crust.
Tap the pan gently on the counter to release bubbles. Run a spatula over the top to smooth.
Bake with a water buffer. Place the springform on a baking sheet. Set a separate pan of hot water on the rack below to create steam.
Bake 45–55 minutes, until edges are set and the center has a slight wobble.
Cool gradually. Turn off the oven, crack the door, and let the cheesecake sit for 30 minutes. Then remove to a rack and cool to room temperature.
Chill fully. Cover and refrigerate at least 6 hours, preferably overnight. This sets the protein and improves texture.
Make the salted caramel. In a small saucepan, combine sugar and water over medium heat.
Swirl (don’t stir) until the mixture turns a deep amber, 6–8 minutes. Remove from heat, carefully whisk in butter and milk, then stir in vanilla and salt. Cool to room temperature; it will thicken as it cools.
Finish and serve. Unmold the cheesecake.
Spoon or drizzle salted caramel over the top, letting some drip down the sides. Sprinkle with a pinch of flaky sea salt. Slice with a warm, dry knife for clean edges.