Preheat the oven to 340°F (170°C) and prepare a 6-inch round cake pan by lining the bottom and sides with parchment paper.
In a large stainless steel or glass mixing bowl, whisk the Greek yogurt until completely smooth and free of any lumps.
Slowly pour the sweetened condensed milk into the yogurt while continuously whisking to ensure a homogeneous emulsion.
Pour the mixture into the prepared cake pan and tap the pan firmly against the countertop 3-5 times to release any trapped air bubbles.
Place the cake pan into a larger deep baking dish. Fill the outer dish with hot water until it reaches halfway up the sides of the cake pan to create a bain-marie (water bath).
Bake for 30 to 35 minutes, or until the edges are firmly set but the center remains slightly jiggly like gelatin.
Remove from the oven and the water bath. Allow the cheesecake to cool to room temperature in the pan for 30 minutes.
Transfer the pan to the refrigerator and chill for at least 4 hours (ideally overnight) to allow the proteins and fats to fully stabilize before unmolding and slicing.