Preheat oven to 350˚F(170˚C).
Line the bottom and sides of a 7" push or springform pan with parchment paper.
In a medium saucepan melt the butter or microwave in a large bowl.
Remove the saucepan from the heat.
Add sugar and cocoa powders. Mix to combine.
In a medium bowl lightly beat the eggs with the vanilla extract.
Add the eggs in three additions alternating with flour.
Pour the batter into the prepared pan.
Bake at 350˚F(170˚C) for 45 minutes. The top should be set and slightly jiggly in the center.
Cool to room temperature before refrigerating for at least 2 hours before serving.