About 30 minutes before serving: In saucepot, prepare pierogi as directed for boiling, using 1 tablespoon salt in water; drain. Meanwhile, thinly slice red peppers and onion. In nonstick 12-inch skillet over medium high heat, in hot salad oil, cook onion 5 minutes. Add red peppers, sugar, vinegar, black pepper and 1/2 teaspoon salt; cook about 10 minutes longer, stirring occasionally, until vegetables are browned and tender. In 1-cup measuring cup, stir flour with 3/4 cup of water until blended; stir into vegetables in skillet; cook 1 minute. Divide pierogi among 3 dinner plates. Spoon pepper mixture over pierogi. Garnish with parsley if you like.