Preheat the oven to 350 degrees.

Place the cake mix, eggs and bananas into a mixing bowl along with the vanilla extract if desired. Beat on high until a smooth batter has formed.

Pour the batter into a well greased loaf pan.

Top with chopped walnuts if desired.

Bake for 40-50 minutes, or until a knife inserted into the center of the bread comes out clean.

If the top begins to brown too much, place some tin foil over the top to prevent it from burning.