Preheat the oven to 350°F.

Grease an 8-inch round cake pan and line the bottom with parchment paper.

In a medium mixing bowl, mix together the flour, cocoa powder, baking powder, and salt. Set aside.

In a large mixing bowl, mix together the eggs and sugar until well combined. Stir in the butter or coconut oil and vanilla. Add the dry mixture to the wet and stir just until combined.

Pour the batter in the prepared pan and bake for 14 to 20 minutes, or until a toothpick inserted in the edge of the cake comes out clean. (A toothpick inserted in the middle will come out wet.) The edges should be crisp and the middle still moist and sticky.

Let the cake cool for 10 minutes in the pan, and then run a paring knife around the edge of the pan. Invert the cake onto a serving plate and remove the parchment paper.

Serve warm, room temperature, or cold.

Store in an airtight container for up to 2 days or refrigerate for 5 days.