Preheat the oven to 350 degrees F. Grease an 8×8 baking pan with butter and line with parchment paper. Set aside.
Heat the butter over medium heat until small brown bits start to appear. Make sure to watch it so it doesn’t burn. Remove from the stove.
Add white chocolate and matcha powder to a small bowl. Pour the brown butter over the top and stir until all the chocolate melts. Let the mixture cool for 2 minutes. This is the ganache mixture.
In stand mixer bowl, combine granulated sugar, brown sugar, eggs, vanilla extract, and salt. Beat until thick and creamy for about 5-10 minutes.
While the machine is on low speed, add the ganache mixture into the mixture.
Sift the flour into the stand mixer bowl. Mix again until combined. Spoon into your prepared baking pan.
Bake for 25-30 minutes until toothpick inserted comes out clean.