For meatballs, preheat oven to 425°F. Line a medium size shallow baking pan with foil or parchment paper; set aside. In a large bowl combine oats, onion, parsley, garlic, salt, black pepper, and cayenne pepper (if using). Add ground turkey; mix well. Shape meat mixture into small meatballs that are about 1 ¼ inches in diameter (about 32 total meatballs). Place meatballs in prepared pan, leaving space between the meatballs.
Bake meatballs for 16 to 18 minutes or until an instant-read thermometer inserted into two stacked meatballs registers 165°F. Set meatballs aside.
Meanwhile, for soup, in a 4- to 6-quart pot, cook carrots and onion in hot oil over medium heat for 6 to 8 minutes or until vegetables are lightly browned, stirring frequently and turning heat down if vegetables brown too quickly. Stir in garlic. Transfer vegetables to a bowl; set aside.
Add broth and potatoes to the same pot. Bring to boiling; reduce heat. Simmer, covered, for 8 minutes.
Add carrot mixture back to the pot along with the kale. Return mixture to boiling; reduce heat. Simmer, covered, for 4 to 6 minutes or until vegetables are just tender.
Stir in undrained tomatoes and the cooked meatballs. Cook for 1 to 2 minutes more or until heated through.