01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a medium bowl, whisk together the flour, baking powder, and salt.
03 - In a large bowl, beat the butter and sugar together until light and fluffy. Add eggs one at a time, beating well after each addition.
04 - Mix in the lemon zest and fresh lemon juice until evenly distributed.
05 - Combine the milk and sour cream in a small bowl and stir until smooth.
06 - Alternate adding the dry ingredients and the milk mixture to the creamed butter, beginning and ending with the dry ingredients. Mix until just combined.
07 - Gently fold the diced strawberries into the batter using a spatula.
08 - Divide the batter evenly among the muffin cups, filling each about two-thirds full.
09 - Bake for 16-18 minutes, or until a toothpick inserted into the center comes out clean. Transfer to a wire rack and cool completely.
10 - Beat the butter on medium speed until smooth. Gradually add the powdered sugar and beat until fully incorporated and fluffy. Add the strawberry puree, lemon juice, and salt, then beat until light and creamy.
11 - Pipe or spread the buttercream onto the cooled cupcakes. Garnish with additional strawberries or lemon zest if desired.