Sauté onion and garlic in hot olive oil in a 3-qt. saucepan over medium-high heat 10 minutes or until tender. Stir tomatoes, Italian seasoning, salt, pepper, and crushed red pepper into onion mixture. Bring to a boil; reduce heat to low, and simmer, stirring occasionally, 1 hour. Let stand 15 minutes. Process tomato mixture in a blender or food processor, in batches, until smooth. Cover and chill up to 5 days. Reheat in a saucepan over medium-low heat.