Bring oil to medium heat in a large pot or Dutch oven. Add the onions and sauté for 5-8 minutes or until tender. Add the chili powder, garlic and cumin and stir to coat the onions. Cook for 2 more minutes. Add the oregano and beans, stir and cook for 30 more seconds. Add the broth and reduce the heat to medium-low. Simmer for 20 minutes, stirring occasionally.

Remove 2 cups of the bean/broth mixture into a blender (or container for an immersion blender) and process until smooth. Return pureed mixture to the pot. Add the chicken and tomatoes and cook over medium-low for another 30 minutes, stirring occasionally. Add the cilantro, lime juice, salt & pepper and stir to combine before serving.