Adjust the oven rack to the middle position and preheat the oven to 350ºF (180ºC). Grease and flour a 9x5 inch loaf pan. You can also line the pan with parchment paper, then grease the parchment paper with cooking spray.
In a large bowl, sift flour, baking powder, baking soda, and salt. Set aside.
In a measuring cup or bowl, mix together lemon juice, milk, and vanilla extract.
Using an electric hand mixer or a stand mixer, beat butter until creamy on medium-high speed, about 3 – 4 minutes. Add the sugar and beat on high speed for 4 minutes until creamed and pale, scraping down the sides and up the bottom of the bowl with a rubber spatula as needed. Add lemon zest and beat for 1 minute.
Turn the mixer to low and add the flour mixture in three batches, alternating with the milk-lemon mixture, beginning and ending with the flour mixture; beat until just combined, about 30 – 45 seconds. Do not overmix.
Pour the batter into the prepared pan. NOTE: The lemon cake batter is thick, so use a spatula to spread it into the pan, if necessary.
Bake for 40 – 45 minutes, or until a toothpick comes out clean when poked in the center. Allow the pound cake to cool for 10 minutes in the pan. Then, remove the cake from the pan and let it cool completely on a wire rack. The cake must be completely cool before frosting.