Position a rack in the center of the oven and preheat the oven to 350°F. Line two muffin tins with paper liners.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
In the bowl of a stand mixer fitted with the paddle attachment, combine the sugar and orange zest. Use your fingers to rub the zest into the sugar—this will infuse the sugar with oils from the zest. Add the butter and oil and beat on medium until light, fluffy, and doubled in volume, 2 to 3 minutes, using a rubber spatula to scrape down the bottom and sides of the bowl as necessary. Reduce the mixer to low and add the eggs one at a time, adding the next egg only after the previous one has been fully incorporated, scraping down the bottom and sides of the bowl after each addition. Add the food coloring and vanilla and beat until the batter is a uniform red color. With the mixer on low, gradually add the dry ingredients in three parts, alternating with the buttermilk, beginning and ending with the dry ingredients. Beat until the last of the dry ingredients are just combined. Scrape down the bottom and sides of the bowl once more and beat for 30 seconds.
Working quickly, place the baking soda in a small ramekin, add the vinegar, and whisk—the mixture will start to bubble and fizz almost immediately. With the mixer on low, pour the vinegar mixture into the cake batter and increase to medium, beating for an additional 30 seconds.
Use a cookie dough scoop to fill each paper liner two-thirds of the way. Bake for 20 to 25 minutes. When done, the top of the cake should bounce back when gently pressed and a skewer inserted into the center of the cake should come out with a few crumbs attached. Cool completely in the pan(s) on a wire rack before frosting.