Line the bottom of a 9-inch springform pan with parchment paper. Brush parchment and sides with butter and dust with a bit of cocoa, discarding any excess.
In a medium bowl, whisk the 10 Tablespoons of melted butter with the sugar, cocoa powder, vanilla, and salt until well mixed. Add the eggs one at a time and whisk until smooth. Fold the flour in to the batter until just until it is combined, then scrape the batter into the prepared pan, smoothing the top.
Bake until the cake forms a thin skin on top but the batter is still loose in the centre, about 10 minutes. Let stand a few minutes, then run a knife around the outside and loosen and remove ring. Slice and enjoy. Left-overs can be refrigerated.
Notes
Note 1:You can make your own cake flour by measuring out 1 cup of all purpose flour, removing 2 Tablespoons of it and replacing with 2 Tablespoons of cornstarch.Whisk together and use in recipe.