Step 1

Preheat oven to 375º F and lightly grease two 9-inch cake pans with butter or non-stick spray.

Step 2

Whisk together flour, sugar, cocoa powder, baking soda and salt in a large bowl, then whisk in water, oil, cider vinegar, coffee and vanilla extract.

Step 3

Stir until no lumps remain, then pour mixture evenly into greased cake pans.

Step 4

Place in oven and bake for 24-26 minutes, or until toothpick inserted in center comes out clean.

Step 5

While cake bakes, make frosting by whisking together powdered sugar, cocoa powder and salt, if using, in a large bowl or mixer.

Step 6

Add water, softened butter and vanilla extract, and beat together until smooth and creamy. Add more sugar for a thicker frosting and more water for a thinner frosting.

Step 7

Remove cake from oven and let cool before frosting.