In a light-colored skillet over medium heat, melt 10 tablespoons salted butter. Cook, stirring often, until it turns golden brown and smells nutty, about 3 to 4 minutes. Pour into a bowl and let cool completely.

Preheat your oven to 350 degrees F. Spray a 9x13-inch glass baking dish with nonstick cooking spray.

In a large mixing bowl, use an electric mixer to beat together the cooled brown butter, 1 1/4 cups granulated sugar, and 1 cup packed brown sugar until well combined.

Add 4 eggs and 1 tablespoon vanilla extract, mixing until smooth.

Add 1 teaspoon salt, 1 teaspoon baking powder, and 2 cups all-purpose flour. Mix just until incorporated; do not overmix.

Fold in 1/2 cup white chocolate chips and 1/2 cup chopped pecans, if using.

Spread the batter evenly in the prepared dish.

Bake for 35 to 40 minutes, until the edges are set and a toothpick inserted near the center comes out mostly clean.

Let cool slightly in the pan before slicing. Serve warm or at room temperature.