Sauté Vegetables: Heat the olive oil in a large over medium heat. Add the onion, carrots, and celery, and cook for 5-7 minutes until softened.
Add Aromatics: Stir in the minced garlic and cook for one more minute until fragrant. Then, add the diced potato and stir everything together.
Combine and Simmer: Add the rinsed lentils, vegetable broth, rosemary sprigs, and thyme. Bring the mixture to a boil, then reduce the heat, cover, and simmer.
Cook Until Tender: Let the soup simmer for 25-30 minutes, or until the lentils and potatoes are tender. Make sure not to overcook the lentils.
Finish and Serve: Remove the rosemary sprigs from the pot. Stir in the fresh lemon juice and season with salt and pepper. Serve hot and enjoy!