Preheat the oven to 350 degrees F.
Grease a 10 cup bundt pan by brushing 1 tablespoon of softened butter all over with a pastry brush. In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
In a large glass measuring cup, combine the buttermilk, yogurt, vanilla, vinegar, and red food gel. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter and sugar together until light and fluffy, about 2-3 minutes. Mix in the oil and beat on high speed until fully combined. Then, turn the mixer down to low speed and add the eggs one at a time. Scrape down the bowl to ensure everything is evenly incorporated.
Alternate the dry ingredients with the buttermilk mixture in 3 additions, mixing until just combined. Scrape down the bowl with a rubber spatula to ensure everything is evenly incorporated.
Pour batter into the prepared bundt pan, smoothing out the top with a rubber spatula.
Bake the cake for 45-50 minutes or until a toothpick inserted comes out clean.
Allow the cake to cool for no more than 10 minutes in the pan, then immediately turn out onto a wire rack to cool completely.