01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, and salt until evenly distributed.
03 - In a large bowl, beat the room-temperature butter and granulated sugar together using an electric mixer until pale, light, and fluffy. Add the eggs one at a time, beating well after each addition until fully incorporated.
04 - Mix in the lemon zest and fresh lemon juice until evenly blended throughout the batter.
05 - Combine the milk and sour cream in a small bowl and stir until smooth.
06 - Alternately add the dry ingredient mixture and the milk mixture to the creamed butter, beginning and ending with the dry ingredients. Mix on low speed until just combined—do not overmix.
07 - Gently fold the diced fresh strawberries into the batter using a spatula, being careful not to crush the pieces.
08 - Divide the batter evenly among the prepared muffin cups, filling each liner about two-thirds full.
09 - Bake for 16–18 minutes, or until a toothpick inserted into the center of a cupcake comes out clean. Transfer the tin to a wire rack and let the cupcakes cool completely before frosting.
10 - Beat the room-temperature butter on medium speed until smooth and creamy. Gradually add the sifted powdered sugar, beating until fully incorporated and fluffy. Blend in the strawberry puree, fresh lemon juice, and a pinch of salt. Beat until the frosting is light, creamy, and spreadable.
11 - Pipe or spread the strawberry lemonade buttercream generously onto each cooled cupcake. Garnish with fresh strawberry halves or additional lemon zest if desired.