Preheat oven to 180 degrees C. Butter and line a square cake tin.

Cream butter and sugar until light and fluffy. Beat in eggs, bananas and vanilla.

Sift the dry ingredients together.

Mix together the milk and lemon juice.

Alternating, add the dry ingredients and the milk, beating between each addition.

Bake in the oven for approximately 45 mins or until a skewer comes out clean.

Rest in the tin for 5 minutes before turning out onto a wire rack to cool.