Heat the oven to 325°F. Line the bottom of a 9-inch springform pan with parchment and lightly grease the sides.

Beat the cream cheese and sugar until smooth, add the eggs one at a time, and mix in the sour cream and vanilla. Pour the batter into the prepared pan and bake for 35–45 minutes, until the center is just set but still slightly wobbly.

Cool the cheesecake completely, then refrigerate it until firm. For easier handling, freeze the chilled layer for 1–2 hours before assembly.

Heat the oven to 350°F and grease and line two 9-inch round cake pans. Whisk together the flour, sugar, baking soda, cocoa powder, and salt.

In a separate bowl, whisk the eggs, oil, buttermilk, red food coloring, vanilla, and vinegar. Add the wet mixture to the dry ingredients and mix only until combined.

Divide the batter between the prepared pans and bake for 25–30 minutes, until a toothpick comes out with a few moist crumbs. Cool the cakes in their pans for about 10 minutes, then transfer them to a rack to cool completely.

Beat the cream cheese and butter until smooth and creamy. Gradually add the sifted powdered sugar, then beat in the vanilla and optional pinch of salt, adding a little more powdered sugar if needed for consistency.

Level the red velvet layers if necessary. Place one cake layer on a serving plate, spread on a thin layer of frosting, carefully add the chilled cheesecake layer, and top with the second red velvet layer.

Apply a thin crumb coat, refrigerate the cake for 20–30 minutes, and then cover it with the remaining frosting. Refrigerate for at least 1 hour before slicing.