Preheat oven to 350 degrees F. Line muffin tins with paper liners.
Sift cake flour, baking powder, and salt into the bowl of a stand mixer. Add the lemon zest, and, using the paddle attachment, mix together briefly on low speed.
With the mixer on medium-low, add the butter, one piece at a time, letting each piece incorporate before adding the next. Mix in the sugar and then increase the speed to medium and mix until the mixture looks like fine, sandy crumbs with a few larger pieces, about 3 minutes.
Add in the eggs, one at a time, beating well after each addition.
Combine the milk, lemon juice, and vanilla in a liquid measuring cup. Pour the milk mixture into the batter and beat on medium speed for about 1 minute, scraping down the sides of the bowl as needed.
Scoop batter into cupcake wells, filling each a little over half full. Bake cupcakes for 14-15 minutes, until a tester inserted into the center comes out with just a few crumbs attached. Let cool in pan for 10 minutes, then remove to wire rack to cool completely before filling and frosting.