Heat oil in a large stockpot over medium-high heat. Add onion, carrots and celery. Saute for 7 minutes, stirring occasionally, until the onion is soft and translucent. Add garlic and sautee for an additional minute or two until fragrant.
Add in remaining ingredients, and stir to combine. Use a long spoon to crush the tomatoes. Bring to a boil, then reduce heat to medium-low and simmer partially-covered for 10 minutes. Season with additional salt and pepper if needed.
Serve with freshly-grated Parmesan cheese.
**Or, you can add all ingredients except the cheese to a slow cooker, stir to combine, cook on high for 3-4 hours (or low for 6-8), then serve with freshly-grated Parmesan cheese.**