Preheat oven to 350°F (175°C) and line a 9x13-inch pan with parchment paper.
In a bowl, whisk melted butter and brown sugar until smooth.
Beat in eggs, vanilla extract, and lemon zest until combined.
In another bowl, mix flour, baking powder, and salt.
Gradually fold dry ingredients into wet mixture until just combined.
Gently fold in chopped strawberries and lemon juice.
Pour batter into prepared pan and spread evenly.
Bake for 28–30 minutes or until a toothpick comes out clean.
Cool completely in the pan before cutting into squares.
