Preheat oven to 325 degrees F. Grease and flour a 10-cup bundt pan.
Begin by making the cheesecake layer. Add cream cheese, cornstarch, sweetened condensed milk, egg, and vanilla extract to a blender or food processor. Blend on high speed or process until completely smooth. Set aside.
8 ounce cream cheese, 1 tablespoon corn starch, 1-14 ounce can, 1 egg, 2 teaspoons vanilla extract
In a large glass measuring cup or mixing bowl, combine oil, eggs, buttermilk, red food coloring, vinegar, and vanilla extract. Whisk until well combined.
1 2/3 cups oil, 2 eggs, 1 cup buttermilk, 2 tablespoon red food coloring, 2 teaspoons white vinegar, 1 teaspoon vanilla extract
In a separate large mixing bowl, combine flour, sugar, cocoa powder, baking soda, and salt. Pour in the wet ingredients and whisk until you have a smooth batter. There should be no clumps or dry spots of flour.
2 1/2 cups all-purpose flour, 2 cups sugar, 3 tablespoons cocoa powder, 1 teaspoon baking soda, 1 teaspoon salt
Pour the batter into the prepared bundt pan, then pour the cheesecake filling evenly over the top. Place the pan in your preheated oven and bake for 1 hour-1 hour 15 minutes. Baking times will vary depending on the pan you use and your oven, so check the cake at the 1 hour mark and then every 5 minutes after than until a wooden skewer inserted into the center comes out clean.
Remove the cake from the oven and allow it to cool on a wire rack for 15 minutes. After 15 minutes remove the cake from the pan and allow it to cool completely.
To make the glaze, whisk together powdered sugar, cocoa powder, and milk until smooth. Mix in Nutella until well combined. If your glaze is too thick, add 1 tablespoon of milk at a time until it reaches a pourable consistency. If it is too thin, add 1 tablespoon of powdered sugar at a time until it thickens. Pour the glaze over the cake and enjoy.
3/4 cup powdered sugar, 2 tablespoons cocoa powder, 3 tablespoons milk, 3 tablespoons Nutella