Preheat the oven to 350°F and line a 9-inch square pan with parchment paper.
Beat the softened butter and sugar until creamy and light, then mix in the egg.
Beat in the lemon juice. A slightly separated appearance is normal.
Whisk together the flour, baking powder, and salt, then stir them into the wet mixture just until combined.
Fold in the diced strawberries and spread the thick batter evenly in the pan.
Bake for 30 to 35 minutes, until the edges are golden and the center is set with moist crumbs.
Cool completely. Whisk the powdered sugar, strawberry puree, and lemon juice into a smooth glaze, spread over the blondies, and let set before slicing.