Preparing Your Workspace:
Preheat your oven to 350°F (175°C).
Generously butter the bottom and sides of a 9-inch springform pan, then dust with flour and tap out any excess.
Remove cream cheese and eggs from refrigerator to bring to room temperature.
Making the Red Velvet Cake Layer:
Prepare the red velvet cake batter according to box instructions until smooth and well combined.
Pour the batter into the prepared springform pan and spread evenly with a spatula.
Tap the pan gently on the counter to release air bubbles.
Bake on the center rack for 30-32 minutes, until a toothpick inserted in the center comes out clean.
Remove from oven and place on a wire rack. Let cool completely for about 30 minutes.
Creating the Cheesecake Layer:
In a large bowl, beat the softened cream cheese with an electric mixer on medium-high speed until smooth and creamy.
Gradually add granulated sugar and continue beating for 2-3 minutes until light and fluffy, scraping down the bowl sides occasionally.
Add eggs one at a time, beating each egg until fully incorporated before adding the next.
Add sour cream, flour, vanilla extract, and salt. Mix on low speed until just combined. Do not overmix.
Pour the cheesecake mixture over the cooled red velvet cake layer and spread evenly to the edges.
Tap the pan gently to remove any air bubbles.
Baking the Combined Layers:
Return the pan to the 350°F oven and bake for 60 minutes, until edges are set but the center still jiggles slightly (about a 2-inch diameter circle).
Turn off the oven but leave the cheesecake inside with the door closed for 10 minutes.
Crack the oven door open slightly and leave for another 10 minutes.
Remove to a wire rack and let cool at room temperature for 30 minutes.
Transfer the entire pan to the refrigerator and chill for at least 4 hours or overnight (overnight is preferred).
Preparing the Whipped Cream Topping:
Just before serving, add cold heavy cream to a medium mixing bowl.
Add powdered sugar and vanilla extract.
Beat on medium speed with an electric mixer, gradually increasing to high speed as cream thickens.
Beat for 3-5 minutes until soft peaks form. Do not overbeat.
Assembling and Serving:
Remove chilled cheesecake from refrigerator and run a knife around the edge of the pan.
Carefully remove the springform pan sides.
Spread the whipped cream evenly over the top of the cheesecake using an offset spatula.
For clean slices, dip a sharp knife in hot water, wipe dry, and cut in one smooth motion. Wipe knife clean between each cut.