1 tbsp [15 ml] olive oil
1½ cups [375 ml] chopped onions
1½ cups [375 ml] chopped peeled carrots
3 large garlic cloves, minced
2½ tsp [7.5 ml] ground cumin
10 cups [2.4 L] (or more) vegetable broth
2/3 cup [160 ml] pearl barley
14½ oz [430 ml] can diced tomatoes in juice
2/3 cup [160 ml] dried red lentils
4 cups [1 L] (packed) coarsely chopped Swiss chard (about 1/2 large bunch)
Heat oil in heavy large nonreactive pot over medium-high heat. Add onions and carrots; sauté until onions are golden brown, about 10 minutes. Add garlic and stir 1 minute. Mix in cumin; stir 30 seconds. Add 10 cups broth and barley; bring to boil. Reduce heat; partially cover and simmer 40 minutes. Stir in tomatoes with juice and lentils; cover and simmer until barley and lentils are tender, about 15 minutes.
Add chard to soup; cover and simmer until chard is tender, about 5 minutes. Season soup with salt and pepper. Thin with more broth, if desired.