Directions

1. Preheat oven to 350F (175C). Grease a 9x13-inch sheet pan.
2. In a large bowl, whisk flour, sugar, cocoa powder, baking soda, and salt.
3. In a saucepan, melt butter with water and bring to a boil.
4. Pour hot butter mixture over dry ingredients and stir to combine.
5. Add buttermilk, eggs, and vanilla; mix until smooth.
6. Pour batter into prepared pan and bake 25 minutes until a toothpick comes out clean.
7. While cake bakes, prepare frosting by melting butter in a saucepan over medium heat.
8. Add powdered sugar, cocoa powder, milk, and vanilla; stir until smooth and thickened.