Preheat Oven to 325 F (162 C). Line a 12 muffin pan with paper cups.
In a medium bowl, hand whisk together sifted flours, salt, and baking agents. Set aside.
Place butter and sugar in the bowl of a stand mixer. Beat on medium with paddle attachment until fluffy. Scrape around the edges and across the bottom once or twice to make sure everything is incorporated.
Add lemon zest and eggs one at a time while continuing to mix on medium low speed.
Slowly spoon half the flour into mixture at low speed. Scrape the sides and bottom of the bowl with a rubber spatula.
Continue on medium speed alternating between spooning in flour and pouring in milk and lemon juice. Mix until a smooth cake batter is formed.
Spoon batter into cupcake papers, filling each one to the top.
Bake for 20-25 minutes or until toothpick comes out clean after being inserted down the center.
Place cupcake pan on cooling rack to cool 10-15 min.. Remove each cupcake and place on rack to cool completely.
Now make your frosting!