Preheat oven to 350°F. Line a 12-cup muffin pan with paper liners.
Blend fresh strawberries to a smooth puree, then measure 1/2 cup and set aside.
Whisk flour, baking powder, baking soda, and salt in a bowl.
Cream softened butter with sugar until pale and fluffy, about 2 minutes.
Beat in the eggs gradually, then mix in vanilla and lemon zest.
Add dry ingredients in two additions, alternating with milk. Mix just until combined.
Fold in the strawberry puree gently to keep the batter airy.
Divide batter among liners, filling each about two-thirds full.
Bake 17–20 minutes, until a toothpick comes out clean. Cool 5 minutes, then transfer to a rack to cool completely.
Beat frosting butter until smooth and creamy, about 1 minute.
Add confectioners' sugar in two batches, mixing on low, then beat in strawberry powder, vanilla, and salt.
Stream in heavy cream a little at a time until fluffy and spreadable, 1–2 minutes on medium.
Swirl or pipe strawberry buttercream onto cooled cupcakes.