Rinse lentils thoroughly, sorting out any debris.
Heat heavy pot or Dutch oven on medium heat.
Add oil, onion, celery, and ground turkey, crumbling and chopping up turkey into smallish pieces. Stir frequently while meat and veggies cook.
Cook about 10 minutes or until meat is browned and vegetables are softened.
Once meat is browned, add the broth, lentils, carrot, black pepper, diced tomatoes, marjoram, and paprika. (I like to add the salt near the end, as sometimes it can hinder the beans from softening properly.)
Bring soup to a light boil, then lower heat to low-medium (about 2-3) and cover for 45-50 minutes or until lentils and carrots are softened. (Note that you will want to stir the pot about every 10 minutes to make sure it's not simmering too hard and nothing is sticking to the bottom of the pot.)
Add salt and taste. Add more salt as desired. (Note that I typically will call for less salt in my recipes, as it's easier to add more but very difficult to fix once you have too much salt).
Serve hot with your favorite crusty bread and salad.