Ensure that the oven is preheated to 300°F. In a 13x9-inch baking dish, grease the bottom and sides.
In a large bowl, combine the flour, sugar, salt, cocoa, baking soda, and baking powder.
To make the eggs bright yellow and slightly thick, beat them with an electric mixer.
When the oil, coffee, and vanilla are combined with the eggs, mix well until well combined.
By alternating with the buttermilk, add the flour to the mix, mixing well after each addition.
After starting with flour, move on to buttermilk, flour, and buttermilk, and end with flour.
In the prepared baking pan, pour the batter. For one hour, bake at 300 degrees. Use a toothpick to check if it is done.