Heat oil in a big soup pot.
Add onion, garlic, and bell pepper.
Cook for 5 minutes until soft.
Add chicken broth and diced tomatoes.
Stir in cumin, chili powder, salt, and pepper.
Bring soup to a boil, then lower the heat.
In a bowl, mix cornmeal, masa harina, baking powder, and salt.
Add oil and chicken broth. Mix to make a soft dough.
Drop spoonfuls of dough into the hot soup.
Cover and cook for 10-12 minutes.
Add chicken if using, and cook for 5 more minutes.
Top with cilantro before serving.