Preheat oven to 325°F. Generously spray a 12 cup Bundt pan with baking spray with flour.
In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt.
In a large bowl, beat butter and sugar together with an electric mixer until fluffy, about 3 minutes. Add vegetable oil and beat 1 minute longer, until combined.
Add eggs, one at a time, beating well after each addition. Stop and scrape down the bottom and sides of the mixing bowl as needed.
Add flour mixture alternately with buttermilk, starting and ending with flour.
Beat in vanilla, vinegar, and food coloring (tint to desired shade) just until combined.
Pour batter into prepared pan and tap lightly on the counter to release any bubbles. Smooth the top of the batter with a spatula.
In a small bowl, mix beat together the cream cheese, confectioners sugar, and vanilla.
Add cream cheese mixture in dollops to cake butter. Use a toothpick to swirl.
Bake 55-65 minutes or until a wooden pick inserted into the center of the cake comes out clean and the top of cake springs back when touched.
Let cool in pan on cooling rack 10 minutes, then turn out onto cooling rack to cool completely.
Sprinkle with powdered sugar and serve.