Rub steak with ground pepper and season with 1/4 teaspoon salt.
Heat a large, heavy skillet (I use my old cast iron skillet) over medium-high heat; when hot, add 1 tablespoon of the oil, then add the steak.
Cook about 7 minutes per side for medium-rare; remove from skillet and place on a serving platter, cover loosely with foil and keep warm.
Pour off any fat from skillet and add remaining 2 tablespoons of the oil; add onions to the skillet, saute about 4 minutes, or until soft and slightly browned; add sliced peppers, garlic and basil; saute about 10 minutes, or until the peppers are soft.
Add balsamic vinegar and give it a few stirs.
Slice the steak into 1/2-inch thick, diagonal slices; dump the onion/pepper mixture on top of the steak slices and dig in.