Preheat oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment paper and lightly grease.
In a large bowl, whisk melted butter and sugar until smooth and glossy.
Add eggs and vanilla extract; mix until fully combined.
Stir in strawberry cake mix, flour, and salt until just combined.
Fold in white chocolate chips if using.
Spread batter evenly into the prepared pan.
Bake for 25–30 minutes, or until the center is set and a toothpick comes out with moist crumbs.
Cool completely before slicing and serving.