01 - Preheat oven to 350°F (175°C). Line a standard 12-cup muffin tin with paper cupcake liners.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until evenly distributed.
03 - In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer on medium speed until the mixture becomes pale, light, and fluffy.
04 - Add the room-temperature 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 throughout the batter.
06 - Add the dry ingredient mixture to the wet ingredients in three additions, alternating with the whole milk in two additions, beginning and ending with the dry ingredients. Mix until just combined—do not overmix.
07 - Gently fold the diced fresh strawberries into the batter using a spatula, taking care not to overmix so the strawberries maintain their shape.
08 - Divide the batter evenly among the prepared cupcake liners, filling each liner approximately two-thirds full to allow room for rising.
09 - Bake on the center oven rack for 16–18 minutes, or until a toothpick inserted into the center of a cupcake comes out clean. Rotate the pan halfway through for even baking.
10 - Remove the cupcakes from the muffin tin and transfer to a wire cooling rack. Allow them to cool completely before frosting—about 45 minutes to 1 hour.
11 - In a mixing bowl, beat the softened butter on medium-high speed until smooth and creamy. Gradually add the sifted powdered sugar, beating on low speed until incorporated, then increase to medium-high. Add the fresh lemon juice, strawberry puree, vanilla extract, and a pinch of salt. Beat until the frosting is light, fluffy, and well combined.
12 - Once the cupcakes are completely cooled, frost each one with the strawberry lemonade buttercream using a piping bag or offset spatula. Garnish with thin strawberry slices or a sprinkle of lemon zest if desired.