Preheat oven to 350 degrees F.
Spray a 9 x 5 loaf pan with baking spray. Mix together your wet ingredients first. Slowly add the dry ingredients until fully incorporated. Mix in zest last. Pour batter into pan.
Bake for 50-55 minutes.
Cool completely before frosting
Beat together the butter and sugar. Stir in lemon juice and extract. Mix until smooth. Add a little milk to adjust consistency to your liking. Frost top of cooled loaf cake.