Preheat oven to 350 degrees. Line a 12-cup muffin pan with cupcake liners.
In a large bowl, beat the butter and sugar together.
Add eggs and vanilla extract until combined.
In a medium bowl, whisk the flour, baking powder, and salt together.
Slowly pour the dry ingredients into the wet ingredients while mixing. Then add the milk, lemon juice, and lemon zest and store until combined.
Spoon batter into 12 cupcake liners, evenly. Bake for 20 minutes. Remove from pan and let cool, then frost the cupcakes with vanilla buttercream.