- Preheat oven to 350°F (177°C). Grease your bundt pan (canned spray works well).
- Make the cake: Whisk the Rogers No Additive All Purpose Flour, baking soda, cocoa powder, and salt together in a large bowl. Set aside.
- Using a handheld or stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed until combined, about 1 minute. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. Add the oil, egg yolks, vanilla extract, and vinegar and beat on high for 2 minutes. (Set the egg whites aside.) Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed.
- With the mixer on low speed, add the dry ingredients in 2-3 additions alternating with the buttermilk. Beat in your desired amount of food coloring just until combined. I use 1-2 teaspoons gel food coloring. Vigorously whisk or beat the 4 egg whites on high speed until fluffy peaks form as pictured above, about 3 minutes. Gently fold into cake batter. The batter will be silky and slightly thick.
- Pour batter into cake pan. Bake for 45-50 minutes or until the tops of the cake springs back when gently touched and a toothpick inserted in the center comes out clean. Remove cake from the oven and let it cool for 10 minutes.
- Invert onto cooling rack.
- Sift icing sugar over top of cake and add garnish of your choosing.