How can I make a delicious dish using onion in tomato sauce?

To make a delicious dish using onion in tomato sauce, start by sauting chopped onions in olive oil until they are soft and translucent. Then, add crushed tomatoes, garlic, herbs like basil and oregano, and a pinch of sugar to balance the acidity of the tomatoes. Let the sauce simmer for about 20-30 minutes to allow the flavors to meld together. You can then use this flavorful tomato and onion sauce as a base for pasta dishes, meatballs, or even as a topping for grilled vegetables.