Spinach Stuffed Shells - cooking recipe

Ingredients

2 Tbsp. salad oil
1 small onion, diced
1 (28 oz.) can tomatoes
1 (6 oz.) can tomato paste
2 tsp. brown sugar
1 tsp. oregano leaves
1 tsp. salt (optional)
pepper to taste
1 (12 oz.) pkg. jumbo macaroni shells
2 (9 or 10 oz.) pkg. frozen creamed spinach in boilable bag
1 (15 or 16 oz.) container Ricotta cheese (2 c.)
1 (8 oz.) pkg. Mozzarella cheese, shredded
1/4 c. Parmesan cheese
1/4 c. fresh parsley

Preparation

About 1 1/2 hours before serving:
In a 3-quart saucepan, over medium heat, in hot oil, cook onion until tender, stirring often. Add tomatoes with their liquid, tomato paste, brown sugar, oregano, 1 teaspoon of salt and 1/4 teaspoon pepper, stirring to break up tomatoes.
Over high heat, heat to boiling.
Reduce heat to low.
Cover and simmer 20 minutes to blend flavors.