Preheat oven to 350º with rack in the center. Spray an 8inch round cake pan with non-stick spray.
Whisk together flour, sugar, cocoa, baking soda, and salt in a large mixing bowl.
Combine water, oil, vinegar, instant coffee, and vanilla in a large measuring cup.
Add to the dry ingredients and whisk just until combined, a few lumps are OK and the mix will be dense.
Poor into pan, then bake until a toothpick inserted in the center comes out clean, 35-45 minutes. Cool cakes on a rack for 15 minutes, then invert onto the rack. Leave cakes upside down (this flattens domed cakes) to cool completely.
In the mean time in a small saucepan combine all topping ingredients and cook over medium-high heat, until cranberries start to release their juice and the liquid thickens and becomes syrupy, 6-7 minutes; cool until needed.