Add vegetable broth and lentils into a large pot, cooking on high heat until it boils. Reduce heat to medium, cover and simmer for 20 minutes.
Heat olive oil in small skillet over medium heat, add in garlic, onion, carrot and celery, stirring until the vegetables are soft, about 5-7 minutes.
Add garlic, onion, carrots and celery into lentil pot and stir. Add cumin, turmeric, salt and pepper to pot and stir again. Simmer for 10 more minutes, or until lentils are soft.
Remove pot from burner. If you want a chunky soup move to the next step. If you want a smooth soup use an immersion blender, or carefully transfer to a blender to blend. Blend until smooth. Be very careful, the soup is hot!
Add lemon juice to pot, stir, and serve. I love serving this with basmati rice and naan.