Bake 8 to 10 minutes or until cod flakes easily when tested with a fork.
Or until until the fish reaches an internal temperature of 145 degrees.
Meanwhile prepare nectarine.
Heat the butter and oil in a large skillet over medium heat saute onions, peppers and garlic for 5 minutes.
Add the nectarines and saute them until they their juices reduce and begin to thicken, 2 to 3 minutes. Sprinkle the sugar over them and saute until the juices further thicken and the sugar caramelizes slightly, about 1 minute.
Add the balsamic vinegar and saute until the juices thicken. Toss in fresh herbs of choice.