Preheat the oven to 180 °C.

Brush a 20cm round cake tin with melted butter or oil.

Beat together softened butter and sugar until fluffy and creamy.

Slowly add the eggs, beating well after each addition.

Add the vanilla and banana puree and whisk them together.

Put the mixture in a large bowl.

Dissolve the baking soda in the milk.

Fold in the sifted flour alternating with the milk through it.

Stir until all is just mixed and the mixture is smooth.

Spoon into the tin and smoothen the mixture.

Bake 1 hour or until a skewer that you put into the middle comes out clean again. If he is still damp inside, let him a little longer in the oven.

Let the cake for 10 minutes in the mold. Let it cool down.