How to Make It
In a large bowl, gently mix the ground beef with half of the minced garlic, 1 cup of the chopped onion, 1 cup of the chopped bell peppers, the oregano, cumin, 1 teaspoon of salt and the egg. Add the cornmeal in 2 batches, mixing gently until combined. Shape the meat mixture into 1 1/2-inch meatballs. Transfer to a plate and refrigerate.
In a medium stockpot, heat the oil until shimmering. Add the remaining minced garlic and cook over moderate heat until golden, about 30 seconds. Add the remaining chopped onion and cook, stirring, until softened, about 4 minutes. Add the remaining chopped bell peppers and cook, stirring often, for 3 minutes longer. Add the tomatoes and cook until softened, about 5 minutes. Add the carrot and cook, stirring, for 1 minute. Add the water, cilantro sprigs and 2 teaspoons of salt and bring the soup to a boil. Reduce the heat to moderately low and simmer for 10 minutes. Add the rice and simmer for 10 minutes longer.
Add the meatballs to the soup and simmer over moderately high heat until they are cooked through and the rice is tender, about 15 minutes. Skim the fat from the surface of the soup and season with salt and pepper. Ladle the meatball soup into bowls and garnish with the chopped cilantro. Serve the soup with lime wedges.