01 - Preheat oven to 350°F (175°C). Line a standard 12-cup muffin tin with 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 unsalted butter and granulated sugar together using an electric mixer until the mixture becomes pale, light, and fluffy.
04 - Add the room-temperature eggs one at a time, beating thoroughly after each addition until fully incorporated before adding the next.
05 - Mix in the fresh lemon juice and finely grated lemon zest until evenly combined throughout the batter.
06 - Gradually add the dry ingredient mixture to the wet ingredients, alternating with the whole milk. Begin and end with the dry ingredients, mixing until just combined. Avoid overmixing.
07 - Gently fold the diced fresh strawberries into the batter using a spatula, taking care not to overmix and break apart the fruit.
08 - Divide the batter evenly among the prepared cupcake liners, filling each liner approximately two-thirds full.
09 - Bake on the center rack 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 cooling rack. Allow to cool completely before frosting.
11 - Beat the softened unsalted butter until smooth and creamy. Gradually add the sifted powdered sugar, beating continuously until the mixture is lump-free. Add the fresh lemon juice, strawberry puree, vanilla extract, and a pinch of salt. Beat until the buttercream is light, fluffy, and fully combined.
12 - Once the cupcakes have cooled completely, frost generously with the strawberry lemonade buttercream using a piping bag or spatula. Garnish with thin strawberry slices or a sprinkle of lemon zest if desired.