In a small bowl, combine your milk and lemon juice and let them sit for a few minutes to sour, to create your "buttermilk."
Preheat your oven to 350 and line a muffin pan with cupcake liners (and lightly spray them with nonstick spray too!).
In a large mixing bowl, beat together your butter and sugar with a hand mixer. Add in your vanilla, lemon zest, and eggs and whisk together again. Lastly, add in your "buttermilk" and mix briefly, till well incorporated.
To the same bowl, add your flour, baking powder and salt. Mix together well until you have a smooth batter.
Fill each cupcake liner about 2/3 way full, filling all 12 liners with the entire cupcake batter.
Bake in the oven for about 18-21 minutes, or till the cupcakes have set on top and a toothpick inserted comes out clean.
In a large mixing bowl, use a hand mixer and combine your butter, lemon juice, lemon zest and vanilla. Pour in your powdered sugar and blend till smooth.
After your cupcakes have cooled, either spread or pipe the frosting onto your cupcakes.
Devour!
Stored in an airtight container, these lemon cupcakes last about 2-3 days.