Preheat the oven to 350 degrees. Spray a 9x9 metal pan with non-stick spray and line it with parchment paper.
In a medium bowl, whisk the flour, cocoa powder, baking powder, baking soda and salt together. Then set aside the dry ingredients.
2 cups (250 g) all-purpose flour, spooned and leveled, ¾ cup (60 g) Dutch process cocoa powder, 1 ½ teaspoon baking powder, ¼ teaspoon baking soda, ½ teaspoon salt
In a large mixing bowl, cream together the butter and granulated sugar with an electric hand mixer on high speed until fluffy, about 3-4 minutes. (If using a stand mixer, use the paddle attachment.) 2 cups (400 g) granulated white sugar, ¾ cup (168 g) unsalted butter, softened
Then add in the eggs and vanilla and mix on medium then medium-high speed until smooth, pale in color and slightly fluffy, about 2-3 minutes. Scrape the sides of the bowl with a rubber spatula as needed.
3 eggs, at room temperature, 1 teaspoon vanilla
Add the dry ingredients and the buttermilk to the butter mixture a little at a time, until all has been added, mixing on low then medium speed for each addition. Mix just until the batter is combined and smooth, scraping the sides of the bowl as necessary.
1 ¼ cups (300 ml) buttermilk, at room temperature
Add in the hot coffee and mix on low speed just until dispersed through the batter.
½ cup (120 ml) hot coffee
Pour the cake batter into the prepared cake. Bake the cake for 48-52 minutes, or until a toothpick comes out clean from the center of the cake. Let the cake cool in the pan on a wire rack to until completely cool.