Cook rice following package directions.
Heat 1 tablespoon olive oil in large nonstick skillet over medium-high heat. Add flank steak slices and sauté for 2 minutes. Remove to a plate and reserve. Drain off all but 1 tablespoon of the liquid in skillet. Add onion slices and cook 5 to 7 minutes, stirring occasionally.
Add curry paste to skillet and cook for 1 minute. Add tomatoes, reserved beef and 1/2 cup water. Bring to a boil. Reduce heat to medium and simmer for 3 minutes, stirring. Serve over rice.