Preheat the oven to 350°F (175°C). Spray a 9 x 13-inch pan with non-stick cooking spray and set it aside.

In a large mixing bowl, whisk together the dry ingredients until evenly combined: 1 ¾ cups flour, 1 ¾ cups sugar, ¾ cup unsweetened cocoa, 2 teaspoons baking powder, 1 teaspoon baking soda, and ½ teaspoon salt.

In a separate bowl or measuring cup, whisk the wet ingredients until blended: 2 eggs, 1 cup coffee (cooled), 1 cup buttermilk, ½ cup vegetable oil, and 1 teaspoon vanilla.

Pour the wet ingredients into the dry ingredients. Beat or whisk for 1–2 minutes until the batter is smooth, scraping down the sides of the bowl as needed.

Pour the batter into the prepared 9 x 13-inch pan and smooth the top. Bake in the preheated oven for 30–40 minutes (about 35 minutes is typical) or until a toothpick inserted into the center comes out clean.

Remove the cake from the oven and place the pan on a wire rack. Let the cake cool in the pan for about 5 minutes.

Using the handle end of a wooden spoon, poke evenly spaced rows of holes across the warm cake to make the "poke" pattern.

Cool the cake in the pan to room temperature before serving. Note: the original directions reference a sweetened condensed milk–chocolate filling and a cocoa/powdered-sugar frosting, but those ingredients are not listed here, so no filling or frosting steps are included.