In a large pot, bring three quarts of water and the lentils to a boil. Reduce the heat to low and let them simmer for 20 minutes.
In a large bowl, combine the ground turkey, breadcrumbs, garlic, half of the diced onion, salt, and pepper. Work the meat with your hands until the ingredients are well-combined.
Using your hands or a cookie scoop, portion and roll out equal-sized meatballs.
Preheat a skillet with a few tablespoons of light olive oil. Place the meatballs in the skillet and brown them on all sides. Remove the meatballs and set the skillet aside.
In the same skillet as you cooked the meatballs, sauté the other half of the diced onion with the diced scallions until the onions are softened and transluscent.
Add the canned diced tomatoes to the skillet, allowing the mixture to come together for a couple of minutes. Add the tomato mixture into the pot with the lentils. Let the soup simmer for 10 minutes.
Using a standard blender or immersion blender, blend the soup until creamy. Place it back into the pot and add in the meatballs.
Let the soup simmer on low heat for 10 minutes. Serve warm and enjoy!