Preheat oven to 325 degrees F. Grease a 8 1/2- by 4 1/2-inch loaf pan with butter or cooking spray.

In a medium bowl, whisk together flour, baking powder and salt. In the bowl of a stand mixer (or a large bowl, using a hand mixer) set on a medium speed, beat together butter, sugar and lemon zest until light and fluffy, 4 to 5 minutes. Add eggs, one at a time, beating to combine after each addition.

Turn the mixer to low and gradually add the flour mixture, milk and lemon juice. Beat until just combined. Take care not to overbeat or the bread will be tough.

Pour the batter into prepared pan and level with a spatula.