In a large Dutch oven, heat 2 tablespoons of olive oil over medium heat. Add the diced onion, carrots, and celery, sautéing for 5-7 minutes until the vegetables are tender.

Stir in the minced garlic and cook for an additional minute. Add the diced russet potato and stir to combine.

Pour in 6 cups of vegetable broth, along with the rinsed French green lentils, fresh rosemary, and thyme. Bring to a boil, then reduce heat to low and cover to simmer for 25-30 minutes.

Check the soup after 25 minutes; the lentils and potatoes should be tender. Cook for a few extra minutes if needed.

Once cooked, remove the rosemary sprigs, stir in 1 tablespoon of fresh lemon juice, and season with salt and pepper. Serve hot.