Preheat your oven to 400°F (200°C) and place a heat-safe skillet or Dutch oven on the bottom oven rack. Boil 4 cups (1 L) water and set aside while you prepare your cheesecake filling.
Place the crème frâiche, granulated sugar, salt in the bowl of an electric-stand mixer fitted with the paddle attachment and beat on low for about 2 minutes or until smooth. Scrape the sides and bottom of the bowl to make sure everything is combined and use the back of a spatula to smash out any lumps.
In a small bowl whisk the eggs plus egg yolk together and then slowly stream them in with mixer on low for about 2 minutes or until combined. Add in the sour cream and lemon juice; making sure each ingredient is well blended before adding in the next. Mix for an additional 2 minutes on low and pour through a fine-mesh sieve into the cooled crust.
Place in the center of the oven and pour the warm water into the skillet on the bottom rack and immediately close the door. Bake the cheesecake for 15 minutes and then reduce the heat 250°F (121°C) for an additional 45 minutes. When done the center will jiggle a bit and the sides will be set. Turn off the oven and let the cheesecake sit in it for 30 minutes with the door open. After 30 minutes, set the cheesecake on the counter and let it sit at room temperature for at least an hour. When cool, wrap tightly in the springform and set in the fridge to chill and set overnight.