01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a medium bowl, whisk together the flour, baking powder, baking soda, and salt until evenly distributed.
03 - In a large bowl, beat the softened butter and granulated sugar together until pale, light, and fluffy.
04 - Add the eggs one at a time, beating well after each addition until fully incorporated.
05 - Mix in the fresh lemon juice and finely grated lemon zest until combined.
06 - Add the dry ingredients to the wet mixture in three additions, alternating with the milk in two additions, starting and ending with the dry ingredients. Mix until just combined — do not overmix.
07 - Gently fold the diced strawberries into the batter using a spatula, taking care not to overmix.
08 - Divide the batter evenly among the prepared cupcake liners, filling each about two-thirds full.
09 - Bake for 16 to 18 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.
10 - Remove the cupcakes from the muffin tin and transfer to a wire rack to cool completely before frosting.
11 - Beat the softened butter until creamy and smooth. Gradually add the sifted powdered sugar, beating until well combined. Add the lemon juice, strawberry puree, vanilla extract, and a pinch of salt. Beat until the frosting is light, fluffy, and fully combined.
12 - Once the cupcakes are completely cool, frost generously with the strawberry lemonade buttercream. Garnish with small strawberry slices or a sprinkle of lemon zest if desired.