8 thick-cut bacon slices, cut into 1⁄2-inch pieces
1 medium-size yellow onion, chopped (1 1⁄2 cups)
2 celery stalks, finely chopped (1⁄2 cup)
3 large garlic cloves, minced (1 1⁄2 Tbsp.)
1 teaspoon ground cumin
1 large sweet potato, peeled and chopped into 3⁄4-inch cubes (3 cups)
1 1/2 cups dried brown lentils
8 cups lower-sodium chicken broth
1 (14.5-oz.) can fire-roasted diced tomatoes, undrained
2 teaspoons kosher salt
1/4 teaspoon black pepper
Chopped fresh flat-leaf parsley
Cook bacon pieces in a large Dutch oven over medium-high, stirring often, until crisp, about 10 minutes. Drain on paper towels, and set aside. Remove and discard all but 2 Tbsp. drippings from Dutch oven.
Add onion, celery, and garlic to Dutch oven. Cook over medium-high, stirring often, until softened, about 5 minutes. Add cumin, and cook, stirring constantly, until toasted, about 1 minute. Stir in sweet potato, lentils, broth, tomatoes, salt, and pepper. Bring to a boil over medium-high. Reduce heat to medium-low; simmer until lentils are tender, 45 to 50 minutes. Spoon soup evenly into 6 bowls. Top with reserved bacon pieces, and sprinkle with parsley.