Mix the eggs, sugar and vanilla together.
Pour the melted butter and buttermilk and mix.
Finally add the flour and baking powder.
Pour the batter into a baking paper-lined baking tin (20x20) and bake the cake at 180 degrees for 20 minutes.
Add the ingredients for the topping in a pan and let them come together into a mixture.
Pour the mixture onto the cake and bake the cake for another 5 minutes.
