Dutch Oven Shrimp

2 Ibs. raw shrimp
1 large onion, finely chopped
1 bottle Italian dressing
1 tsp. red/cayenne pepper, or more to taste
1 tsp. black pepper
2 tbsp. parsley, chopped
2 sticks margarine or butter

Melt margarine in a Dutch oven. Add the rest of the ingredients including the shrimp. Mix well and bake for 45 minutes, rotating a quarter turn every 15 minutes. Serve with a crusty bread.