Preheat oven to 375 degrees F. Generously butter a baking pan, then dust with little flour and tap out the excess.
Meanwhile melt the chocolate and butter in the microwave. Mix well.
Whisk eggs with sugar until frothy and blended.
Add eggs to the chocolate batter and whisk.
Add sifted flour and whisk again.
Pour into prepared cake pan and bake for 25- 30 minutes.
Run the knife along to check if it is ready. Cake should be moist and not dry.
Let it completely cool, remove the cake from the pan. Dust with confectioner's sugar and serve.