Preheat oven to 450°F. Line a rimmed baking sheet with non-stick aluminum foil. Drain tomatoes, reserving the juice. Seed tomatoes, pat dry with paper towels and spread in a single layer on the foil. Sprinkle evenly with 2 teaspoons of brown sugar. Bake until all liquid has evaporated and the tomatoes begin to color, about 20 minutes. Remove from oven; let the tomatoes cool slightly.
Heat olive oil in Dutch oven over medium heat. Add onion, carrots, and celery; cook, until tender, about 10 minutes.
Add roasted tomatoes, lentils, chicken broth, reserved tomato juice, salt, cumin, coriander, pepper, and remaining 2 teaspoons of brown sugar.
Bring to a boil over high heat. If scum develops, skim off and discard. Lower heat to low; cover and cook until lentils are tender, about 50 minutes.
If desired, purée to preferred consistency with a stick blender.
Serve.
Yield: 6 to 8 servings.