Cut the chicken breast into small, bite-sized pieces.
Heat the olive oil in a large pot over medium heat and add the chicken, cooking until lightly browned on all sides.
Add the diced onion, carrots, and celery to the pot, sautéing for 5 minutes until the vegetables begin to soften.
Stir in the minced garlic, cumin, turmeric, salt, and pepper, cooking for 1 minute until fragrant.
Add the dry red lentils and pour in the chicken broth, stirring to combine all ingredients.
Bring the soup to a boil, then reduce the heat to low, cover, and simmer for 15 to 20 minutes until the lentils are tender and starting to break down.
Stir in the baby spinach and allow it to wilt in the hot soup for about 1 minute.
Finish by stirring in the fresh lemon juice to brighten the flavors before serving.