Pre-heat oven to 350°F.
Prepare three 9-inch round cake pans with non-stick spray and/or parchment paper.
In the bowl of stand mixer with whisk attachment, add the granulated sugar and eggs; beat on high for 2 to 3 minutes.
Meanwhile, in a small bowl, combine the hot water, cocoa powder, instant coffee and salt.
With mixer on lowest setting, add to sugar mixture.
With mixer still on low, slowly add in flour, baking soda and baking powder; mix to incorporate.
Add in oil, buttermillk and vanilla extract.
Scrape down sides and bottom of bowl, as needed; do not overmix.
Evenly pour batter into prepared pans; place in pre-heated oven; bake for 22 to 25 minutes, or until an inserted toothpick is removed clean.
Remove from the oven; allow cakes to cool in pans for 10 minutes; then invert onto a wire rack.
Let cakes cool to room temperature or place in refrigerator until ready to assemble.