Step 1

Preheat oven to 350°F or 175°C.

Step 2

Whisk together sugar, potato starch, cocoa powder, baking powder, and salt in a large mixing bowl.

Step 3

Add eggs, oil, and black coffee or water. Mix until well combined. It will seem very liquidy, but it's fine.

Step 4

Use a rubber spatula to pour batter into a 9x13 inch baking pan.

Step 5

Bake for 45 to 50 minutes or until a toothpick comes out clean when poked through the middle.

Step 6

Remove from oven and let cool completely before cutting.