Preheat oven to 350°. Spray a 13x9-inch baking pan with nonstick baking spray with flour.
In a large bowl, combine flour, sugar, baking soda, cinnamon, and salt.
In a medium saucepan, combine butter, Coca-Cola®, buttermilk, and cocoa. Bring to a boil over medium-high heat, whisking constantly. Remove from heat, and add to flour mixture, whisking until smooth. Add eggs and vanilla, whisking until smooth. Spoon batter into prepared pan; bake for 30 to 35 minutes or until a wooden pick inserted in center comes out clean. Pour Coca-Cola® Frosting over hot cake. Let cool for 30 minutes before serving.
Recipe by The Ribbon in My Journal - Phyllis Hoffman DePiano at https://www.theribboninmyjournal.com/cake-memorial-day-crowd/