Some brands of prepared spaghetti sauce are sold in 26-ounce jars; that size works fine for this recipe too.
Sauté onion in hot oil in a Dutch oven 5 minutes; stir in next 3 ingredients. Bring to a boil, stirring occasionally; add salt and pepper to taste. Reduce heat, and simmer, uncovered, 15 minutes.
Note: For testing purposes only, we used 2 (25-ounce) jars Emeril's Roasted Gaaahlic Pasta Sauce.