Preheat the oven to 350 degrees F. and lightly oil around 9-inch spring-form pan. Set aside.
In a large bowl mix the milk and apple cider vinegar. Whisk until it begins to thicken.
Add in the oil and vanilla extract. Mix until well combined.
In a medium bowl combine the flour, cocoa powder, granulated sugar, brown sugar, baking soda, and salt. Mix well and add it into the bowl with the wet ingredients. Add in the red gel food coloring and mix well, but do not overmix.
Pour the batter into the prepared pan and bake for 30 minutes.—or until a toothpick inserted in the center comes out clean.
Remove it from the oven and allow it to cool in the pan over a cooling rack. Release the spring and let it sit until completely cool before trying to fully unmold it from the ring and bottom of the pan.
Optional frost once the cake is fully cooled.
Notes
Don’t over-mix the batter: Otherwise, you may end up with a dense, tough cake. Mix until everything is only just combined.
Adding dye: The type used affects how much is needed - liquid dye usually needs double the gel amount. Adjust to your preferred redness.
Leave it to cool: It’s fragile right out of the oven but sets while cooling. It’s also important that it’s fully cooled before frosting.
For a layered cake: Double the batter and level the cake layers before building and frosting. Save the crumbs to decorate.