Preheat oven to 180 degrees C. Lightly grease a 9x5 inch loaf pan.

In a large bowl, combine flour, baking soda, baking powder and salt. In a separate bowl, cream together butter and sugar. Stir in eggs and mashed bananas until well blended. Add lemon zest and juice. Stir banana mixture into flour mixture; stir just to moisten. Pour batter into prepared loaf pan.

Bake in preheated oven for 60 to 65 minutes, until a skewer inserted into center of the loaf comes out clean. Let bread cool in pan for 10 minutes, then turn out onto a wire rack.