Heat oven to 350°F. Line an 8-inch square pan with parchment and lightly grease.
Whisk the beaten eggs, oil, vanilla, and 2 tablespoons jam in a large bowl.
Add cake mix and salt. Stir until a thick, smooth batter forms; do not overmix.
Fold in white chocolate chips if using.
Spread batter evenly into the prepared pan. Smooth the top.
Bake 17–22 minutes, until set and edges look slightly golden. A few moist crumbs are fine.
Cool in the pan for 15 minutes while you make the glaze.
Whisk powdered sugar, milk, 1 tablespoon jam, and lemon juice until pourable.
Spread glaze over warm brownies. Let set until the glaze firms up.
Slice into 16 squares. Top with diced strawberries just before serving, if desired.