Heat olive oil in a large pot or Dutch oven over medium heat. Add onion and cook until softened, about 5-7 minutes.
Add garlic and cook for another minute until fragrant.
Stir in the rinsed lentils, vegetable broth, diced tomatoes, thyme, and cumin.
Bring the soup to a boil, then reduce heat, cover, and simmer for 30-40 minutes, or until lentils are tender.
Season with salt and pepper to taste.
Serve hot, garnished with fresh parsley if desired.
Notes
This hearty lentil soup is perfect for a quick and nutritious meal. Feel free to add other vegetables like carrots or celery for extra flavor and texture.