Preheat the oven to 350F degrees Fahrenheit. Grease an (8x4 inch or 9x5 inch) loaf pan with cooking spray
In a medium bowl, whisk together the flour, baking powder, lemon zest, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or with an electric mixer), beat the butter and sugar together until fluffy and pale, about 4-6 minutes. With a spatula, scrape the sides and bottom of the bowl as needed.
With the mixer on low-speed, add the eggs one at a time, add the vanilla extract and lemon juice. Beat on medium-high speed until combined.
With the mixer on low, add the flour and buttermilk alternately to the batter, beginning and ending with the flour.
Put the batter into the prepared loaf pan and bake for 45-55 minutes until the cake is golden brown and a toothpick inserted into the cake comes out clean with only a few moist crumbs.
Remove from the oven and allow to cool in the pan for about 15 minutes.
Prepare the lemon syrup by combining together the confectioners’ sugar and lemon juice. Set aside.
Remove the lemon loaf from the pan and set it on a rack. Brush the syrup over the loaf while warm.
Make the icing by whisking together the confectioners’ sugar, lemon juice and milk. Add additional juice, if needed. The icing should be thick.
When the loaf is completely cool, pour the icing over the loaf.