To begin, preheat your oven to a temperature of 350 degrees Fahrenheit (175 degrees Celsius) and apply cooking spray onto 2, 9-inch springform pans.
Next, take a large bowl and sift in the flour, salt, baking soda, and cocoa powder. Proceed to add in the oil, 2 eggs, vanilla extract, vinegar, white sugar, and buttermilk. Once fully combined, whisk in the food coloring and water. Divide the batter equally between the two pans.
Bake the cakes in the preheated oven for approximately 30 minutes, or until a toothpick inserted into the center of the cake comes out clean.
While the cakes are cooling, use an electric mixer to beat the cream cheese in a large bowl until it is smooth. Add in the sugar and cornstarch, and continue to beat until it becomes creamy. One by one, add in the 2 remaining eggs, beating well after each addition. Mix in the vanilla extract and then use a hand whisk to blend in the heavy cream until it is fully combined. Divide the batter equally between the two cake layers.
Bake the cheesecakes in the preheated oven until they are set and beginning to brown, for approximately 30 to 45 minutes. Once done, cool them on a wire rack for 1 hour before covering and placing them in the refrigerator until they are completely cool, for an additional hour.
