01 - Preheat oven to 350°F (175°C). 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 using an electric mixer until pale, light, and fluffy.
04 - Add the eggs one at a time, beating well after each addition to ensure full incorporation before adding the next.
05 - Mix in the fresh lemon juice and finely grated lemon zest until evenly combined.
06 - Add the dry ingredient mixture to the wet ingredients 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, being careful not to overmix and break up the fruit.
08 - Divide the batter evenly among the 12 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. Rotate the pan halfway through baking for even results.
10 - Remove the cupcakes from the muffin tin and transfer to a wire rack. Let cool completely before frosting.
11 - Beat the softened butter until creamy and smooth. Gradually add the sifted powdered sugar, beating on low speed until incorporated, then increase speed and beat until fluffy. Add the lemon juice, strawberry puree, vanilla extract, and salt. Beat until the frosting is light, fluffy, and well combined.
12 - Once the cupcakes are completely cool, frost generously with the strawberry lemonade buttercream using a piping bag or spatula. Optionally garnish with fresh strawberry slices or a sprinkle of lemon zest.