Preheat oven to 350

Butter and lightly flour a 9-inch square cake pan.

Cream the butter, slowly add the sugar, and beat until light.

Add 2 bananas, 2 eggs, & vanilla. Beat well

Mix 2 cups flour, 1 tsp baking soda, & 1/2 tsp salt; add to the first mixture and blend.

Slowly add the sour cream and beat until well blended.

Spread the batter in the pan and bake for 45 minutes, or until a toothpick comes out clean.

Create the banana cream filling while the batter is baking.

Heat the milk in a heavy-bottomed pan until very hot but not boiling.

mix the 1/2 cup sugar, 3 Tbsp flour, and 1/4 tsp salt together in a bowl, stir in the hot milk, and beat until well blended.

Pour back into the pan and continue stirring vigorously over low heat for 4-5 minutes, until very thick and smooth.

add 2 egg yolks and cook for a few more minutes.

Cool the filling mixture.

Mash 1 banana and beat it until smooth.

Add the lemon juice to the mashed banana and stir the mixture into the cooled filling.

Make the Portsmouth frosting.

Mix 1/4 cup butter, cream, and rum together in a bowl.

Slowly beat in the sugar until thick and creamy.

After baking, cool cake in pan for 5 minutes before turning out onto a cooling rack.

Split the cake and fill with the banana cream filling and frost with Portsmouth frosting.