In mixing bowl, combine butter and sugar, mixing until smooth. Add in egg, sour cream, lemon zest, vanilla, lavender extract, and bananas. Mix and set aside.
In separate bowl combine flour, baking soda and powder, and salt. Whisk together until blended.
In loaf pan, grease and then dust the sides with flour. Pour In batter until it fills the pan halfway.
Bake for 40-45 minutes.
Remove and allow to cool briefly. Serve warm or cooled.