Heat olive oil in a large, deep skillet over medium-high heat.
Rinse steak and pat dry. Place in skillet and brown on both sides, about 1-2 minutes per side. Drain off oil.
Add brown sugar, soy sauce, onion, broth, celery, water chestnuts, and pepper. Make sure the the steak and vegetables are submerged in liquid mixture.
Reduce heat and simmer, covered, for 1 hour and 30 minutes or until steak is tender.
Garnish with pimientos before serving.