Coat a nonstick skillet with cooking spray. Place over medium-high heat. Sprinkle the steak with the pepper and salt. Brown for 2 minutes per side. Add 1/2 cup of the broth; cook, turning once, for 5 to 6 minutes per side (for medium-rare). Remove the steak from the skillet; cover the steak loosely to keep it warm. Reduce the heat to medium. Add the onion slices to the skillet and cook until golden brown, about 4 to 5 minutes per side. Add the remaining broth as needed to prevent the onions from sticking.

To Freeze: Freeze in freezer safe container.

To Reheat: Defrost. Reheat sauce over medium heat, add steak to warm.