Prep pans and oven. Grease three six inch round pans and line bottoms with parchment. Heat oven to 350°F.
Dry mix. In a medium bowl whisk flour, cocoa, baking powder, baking soda, and salt until evenly combined.
Wet base. In a large bowl whisk both sugars with eggs until slightly thick and lighter in color, about 2 minutes by hand or on low speed. Whisk in oil, buttermilk, and vanilla until smooth.
Combine. Sift the dry mixture into the wet and whisk gently just until combined. Scrape the bowl.
Bloom cocoa. Slowly stream in hot coffee while whisking on low. The batter will be thin.
Bake. Divide evenly into the pans, about 400 g batter per pan. Tap gently to release bubbles. Bake 25 to 30 minutes until tops spring back and a tester comes out clean.
Cool. Rest 10 minutes in the pans, then turn out to racks and cool completely.