Zest the lemon into the sugar and mix gently with your fingers while rubbing the zest in.
In another bowl, melt together the butter and white chocolate in the microwave in 15 second intervals (to not burn it!).
Once melted and smooth, pour in the sugar/zest mixture into the butter mixture and whisk.
Add in the eggs, vanilla, lemon juice, and mix.
Then add in the salt and flour, and fold gently.
Bake at 350 for about 27-30 min (in a 9x9 pan).
For the glaze, mix together the powdered sugar, 1–3 tbsp lemon juice, and 1 tbsp lemon zest.