Cumin Lentil Barley Stew

I love lentils and barley, but had never before put them together.  They made a delicious combination in this hearty soup.  The leftovers tasted even better the second day (with a little broth thrown in before reheating).  

2 tbsp olive oil
1 large onion, chopped
2 carrots, peeled and sliced
2 stalks celery, sliced
1 tsp salt
2 cloves garlic, minced
2 tsp cumin
1/2 tsp coriander
1 14 oz can diced tomatoes
8 cups chicken or vegetable stock
1 cup lentils, rinsed and picked over
1 cup barley, rinsed and picked over
1 package frozen spinach, thawed and drained
Salt and pepper to taste

Heat oil over medium heat in a large stockpot until shimmering. Add onion, carrots, celery and salt and cook until tender, about 7 minutes. Add garlic, cumin and coriander and stir until fragrant, about 30 seconds.

Stir in tomatoes, stock, lentils and barley. Bring just to a boil. Cover and reduce heat to low. Simmer until lentils and barley are tender, about 40 minutes. Stir in spinach and heat through.

Season with salt and pepper.