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. Set aside.
03 - In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer on medium speed until the mixture is pale, light, and fluffy — approximately 3 minutes.
04 - Add the eggs one at a time, beating well after each addition until fully incorporated before adding the next egg.
05 - Mix in the fresh lemon juice and finely grated lemon zest until evenly combined.
06 - Gradually add the dry ingredient mixture to the wet batter, alternating with the whole milk. Begin and end with the dry ingredients, mixing on low speed until just combined. Do not overmix.
07 - Using a spatula, gently fold the diced fresh strawberries into the batter with minimal strokes to distribute evenly without crushing the fruit.
08 - Divide the batter evenly among the 12 cupcake liners, filling each liner approximately two-thirds full to allow room for rising.
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. Rotate the pan halfway through baking for even results.
10 - Remove the cupcakes from the muffin tin and transfer to a wire cooling rack. Allow to cool completely before frosting — approximately 45 minutes to 1 hour.
11 - In a mixing bowl, beat the softened butter on medium 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 for 2 to 3 minutes until the buttercream is light, fluffy, and well combined.
12 - Once the cupcakes are completely cooled, frost each one generously with the strawberry lemonade buttercream using a piping bag or offset spatula. Optionally garnish with thin strawberry slices or a sprinkle of lemon zest.