Preheat oven to 350F. Line a 9x9-inch baking dish with parchment paper, leaving some sticking up from two sides to make it easier to lift the blondies out of the pan after baking.
In a large mixing bowl, cream together the butter and granulated sugar until light and fluffy, then beat in the egg. Beat in the 1/4 cup fresh lemon juice. Be aware that the lemon juice might not fully incorporate.
In a medium mixing bowl, whisk together the flour, baking powder, and salt. Mix into the wet mixture until well combined. Gently fold in the fresh strawberries.
Scoop the blondie dough into the prepared baking dish and gently spread out evenly.
Bake the blondies at 350F for 30-35 minutes, just until a toothpick inserted into the center comes out clean. Do not over-bake. Let the blondies cool for 5 minutes in the pan, then lift out and cool completely to room temperature before cutting into bars.
In a small bowl, melt the strawberry jelly in the microwave in 15 second increments, just until melted. Add the 1 tablespoon of lemon juice and 1 cup powdered sugar; whisk until smooth. If desired, add a drop or two of red or pink food coloring for brighter color. Drizzle the frosting over top of the cooled blondies.