Heat the oven to 350°F. Line a 9-inch square pan with parchment paper.
Beat the butter and sugar until creamy. Add the egg, lemon zest, and lemon juice.
Whisk together the flour, baking powder, and salt. Stir the dry ingredients into the wet mixture until just combined.
Fold in the diced strawberries, then spread the thick batter evenly in the prepared pan.
Bake for 30 to 35 minutes, until the edges are lightly golden and the center is set with a few moist crumbs.
Cool completely. Whisk the powdered sugar, strawberry puree, and lemon juice into a smooth glaze.
Spread the glaze over the cooled blondies, let it set, then slice and serve.