1. Preheat the oven to 350°F (180°C). Line a 9×9-inch baking pan with parchment paper, leaving an overhang for easy removal.
2. Cream the butter in a large bowl using a hand mixer until smooth.
3. In a separate bowl, whisk together the sugar and lemon zest to release the lemon oils and enhance the sugar’s flavor, then add to the butter mixture and blend well.
4. Add the eggs one at a time, mixing thoroughly after each addition.
5. Melt the white chocolate chips carefully in the microwave, stirring between short intervals until smooth, then blend into the butter mixture along with the fresh lemon juice.
6. Sift together the flour and salt, then gradually add to the wet ingredients, mixing until just combined. Avoid overmixing.
7. Pour the batter into the prepared pan, spreading evenly, and bake for 35-38 minutes. Start checking for doneness at 25 minutes by inserting a toothpick in the center; brownies are done when it comes out with moist crumbs but no wet batter. Cover with foil if the top browns too quickly.
8. Let the brownies cool completely in the pan.
9. For the topping, beat the cream cheese until smooth, and then mix in the powdered sugar, lemon juice, and zest until smooth.
10. Spread the topping over the cooled brownies and refrigerate for at least 30 minutes before slicing for cleaner cuts.