Heat 3 tablespoons of olive oil in a Dutch oven to medium heat. Add onions, carrots, celery, fennel, and bell pepper, cook for 6 to 8 minutes. Stir in garlic, bay leaves, oregano, and cook 1 more minute. Add tomato paste, lemon zest, juice, 1 teaspoon salt, and 1/2 teaspoon of pepper, cook for 2 minutes. Stir in fire roasted tomatoes and chicken broth, bring to a boil, and taste for salt. Reduce the heat to a low simmer.