Make Salted Butterscotch Sauce: Combine the cream of tartar and water in a small bowl. Melt the butter in a medium saucepan over medium heat. Stir in the brown sugar, cream of tartar/water mixture, and heavy cream. Then, let the mixture come to a boil and let it boil for 5 minutes. Do not stir it at all during this time. When the time is up, remove from the heat and stir in the vanilla and a generous pinch of flaky sea salt (to taste). Transfer to a jar or bowl to cool before using.(Store any leftover in the fridge.)

Reduce the Cream Soda: Add the cream soda to a large or medium saucepan and heat over high heat until bubbling - cook, stirring occasionally, until reduced to ½ cup. This will take about 25-32 minutes. Pour the reduced cream soda into a measuring cup and set aside to cool to room temperature. (You can speed this up in the fridge.)

Make the Crust: Preheat oven to 350° F. Spray a 9-inch springform pan with nonstick spray and make sure the bottom is securely fastened. Stir together crust ingredients and press into prepared pan and up the sides of the pan (see photos above). Bake this for 10 minutes. Set aside. Keep the oven on at 350. Fill a large pot with water and set it on your stove, and get out a large roasting pan – you'll need this for your water bath later.

Make the Cheesecake Filling: Remember that your cold ingredients need to come to room temp before you start. In a large mixing bowl, beat the softened cream cheese with electric mixer until creamy, about 1-2 minutes. Add the sugar & mix on high speed until well incorporated, about 1-2 minute. Scrape the sides & bottom of the bowl with a rubber spatula as you go - little lumps of cream cheese love to hide in the bottom of the bowl. Add the eggs one at a time, mixing on medium speed after each until just barely incorporated, and scraping the bottom of the bowl between each addition to catch any lumps. Do not over mix when adding the eggs - this can cause your cheesecake to puff up and inflate then collapse in the oven, or if you really over mix, it can overflow. Add the vanilla, sour cream, butterscotch sauce, cream soda reduction, and butter extract and mix until just combined. Tip: You can also do this in a stand mixer fitted with the paddle attachment.

Prepare the Water Bath + Bake: Bring the large pot of water to a boil. Set your springform pan on a rack positioned in the center of the oven, and place the roasting pan on the rack below, or wrap the base of the cheesecake pan in foil and place it inside a 10-inch cake pan inside the roasting dish. Pour the boiling water into the roasting pan. Both of these methods ensure no leaks.

Bake: Bake the cheesecake for 1 hour and 45 minutes to 2 hours. When done, the cheesecake will have only a slight wobble in the center, and a knife inserted into the edge will come out clean, and will have just a bit of thick batter when inserted into the center. An instant read thermometer should read between 170℉ and 176℉ when inserted into the center/towards the bottom of the cheesecake. Turn off the oven and crack the door open. Let the cheesecake cool in the oven for 1 hour before removing it.

Cheesecake Cooling: Once the hour is up, remove the pan from the oven. It should be cool enough to handle. Remove the foil and set the springform pan on a wire rack. Let cool completely at room temp, then cover with foil and refrigerate at least 6 hours or up to 1 day before removing from the pan and serving.

Make the Whipped Cream: Make the whipped cream just before you're ready to serve the cheesecake. It's best made fresh – not made ahead. If you plan to pipe on the whipped cream, I recommend stabilizing it. Add the water to a small bowl and sprinkle the powdered gelatin on top. Let stand for 3 minutes. Then, microwave for 4-5 seconds, just to re-liquify the mixture. Set aside while you begin the cream. Add the whipped cream ingredients to a medium bowl and beat on high speed until it begins to thicken. Or, use a food processor – this will make the whipped cream easier to pipe! Pulse 10-12, then run on low until cream is just starting to thicken. Stream in the liquid gelatin mixture while you mix on low in either method. Keep mixing/pulsing until cream is thick but still smooth. Add cream to a piping bag (I used a Wilton 6B tip) and pipe on the cheesecake as desired.

Serve & Store: Serve with extra butterscotch sauce on top, and pipe on the whipped cream (or serve it on the side) then slice and enjoy! Store leftovers in an airtight container in the fridge for 3-4 days.