Place the onion, carrot, celery and garlic in a food processor and puree.
Coat the bottom of a heavy stock pot with olive oil and sauté the pureed veggies.
When the veggies just begin to stick to the bottom of the pot add your ground beef and finely break apart using a spatula. Salt the veggies and beef and continue cooking stirring occasionally until browned.
Add the tomato paste once the meat is browned. Cook the paste for a minute or two
Add your pureed tomatoes, pesto and season with salt again if needed.
Cover and simmer for at least 45 minutes. However, the longer you let it simmer the more intense the flavors will be. We like to let it simmer for 2-3 hours if possible and if starts to dry out you can add beef stock to loosen up the sauce again.