Place ground beef, 1/2 of the cilantro, 1/2 of the onion, garlic, garlic salt, and onion powder in a bowl. Sprinkle with salt and black pepper; mix gently until combined. Form meat mixture into golf ball-sized meatballs.
Coat a large skillet with nonstick cooking spray; warm over medium-high heat. Cook meatballs in the hot skillet until browned all over. Transfer meatballs to a plate and set aside. (Meatballs do not need to be fully cooked since they will finish cooking in the soup.)
Cook and stir remaining onion in the same skillet over medium-low heat until translucent, 8 to 10 minutes. Transfer onions to a large pot.
Pour chicken broth into the pot with onions. Stir in carrots, celery, and potatoes. Bring to a boil over high heat; reduce heat and simmer until potatoes are nearly tender, about 15 minutes.
Add meatballs and remaining cilantro; simmer for 30 minutes. Season with salt and black pepper.