Rinse 2 cups dried lentils under cold water in a fine mesh strainer.
Heat a large pot with 3 Tbsp olive oil over medium high heat. Add 1 cup chopped yellow onion, 2 chopped carrots, and 1 chopped celery stalk. Sautee the vegetables for 2 minutes, until onion is translucent. Now add 4 minced garlic cloves, stir in and cook another 30 seconds.
Next add 32 oz vegetable broth, 2 cups dried lentils, 15 oz crushed tomatoes, 1 tsp ground cumin, 1 ½ tsp dried basil, ½ tsp salt and ½ tsp ground black pepper. Stir everything together.
Bring the pot to a boil, then reduce heat to let it simmer. Stir often using a silicone spatula, scraping the bottom of the pan every couple of minutes. Continue to simmer until lentils are cooked (you can check by removing a few and letting them cool, then tasting them). This will take about 5-8 minutes. The soup is now ready to serve.