01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat butter and sugar together until light and fluffy, about 2-3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in lemon zest, lemon juice, and vanilla extract.
05 - Add the dry ingredients in three parts, alternating with the milk, beginning and ending with flour. Mix until just combined; do not overmix.
06 - Divide the batter evenly among the cupcake liners, filling each about 2/3 full.
07 - Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
08 - In a medium bowl, beat the butter until creamy. Add powdered sugar gradually, beating until smooth.
09 - Mix in the strawberry puree, vanilla extract, and a pinch of salt. Beat until fluffy and pink. If the buttercream is too soft, add extra powdered sugar by the tablespoon; if too stiff, add a little more strawberry puree or a splash of milk.
10 - Once cupcakes are completely cool, pipe or spread the strawberry buttercream on top.