Start by preheating your oven to 350°F (177°C) and lining a 12-cup muffin pan with cupcake liners for easy removal.
Cream the butter and sugar using a mixer on medium-high until fluffy, about 2 minutes. Add eggs and vanilla, mixing until just combined.
Whisk together flour, baking powder, and salt. Gradually mix into wet ingredients, then slowly incorporate milk, lemon juice, and zest until just combined.
Fill cupcake liners 2/3 full with batter and bake for 18-22 minutes, or until a toothpick comes out clean. Allow to cool before frosting.
Frost the cooled cupcakes with vanilla buttercream and garnish with lemon zest if desired.