Preheat oven to 400 degrees F. Lightly spray an 9x9-inch square baking dish.
Prepare the broccoli according to the manufacturer's directions. (I use the microwavable steaming packages.) Drain and set aside.
Melt the butter in a medium skillet over medium heat. Add the onions and cook until translucent, about 5 minutes. Remove from heat and set aside to cool.
In a large mixing bowl, mix together the eggs, cottage cheese and salt until well blended. Stir in the muffin mix, onions and broccoli. Mix until just combined.
Spread the batter into the prepared pan. Bake for 20 to 25 minutes or until cooked through and golden. Remove from oven and let sit for 5 minutes before cutting into squares. Serve warm.