1. Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving overhang on two sides.

2. In a large bowl, whisk together melted butter and brown sugar until smooth and glossy.

3. Add egg, egg yolk, vanilla extract, lemon juice, and lemon zest. Whisk vigorously for 30 seconds until well combined and slightly foamy.

4. In a separate bowl, whisk together flour, baking powder, and salt.

5. Pour dry ingredients into wet mixture and fold gently with a rubber spatula until just combined, being careful not to overmix.

6. Pat strawberries dry and dice into quarter-inch pieces. Gently fold into batter.

7. Spread batter evenly into prepared pan.

8. Bake for 28-32 minutes, until edges are golden brown and a toothpick inserted 2 inches from the edge comes out clean. Center should look slightly underdone.

9. Cool in pan for 15 minutes, then lift out using parchment overhang and cool completely on a wire rack before cutting.

10. Dust with powdered sugar if desired and cut into squares.