Puree tomatoes, garlic powder and onion powder in blender or food processor.
Transfer mixture to large Dutch oven over medium/high heat. Cook while stirring until the liquid has reduced by about half, approximately 5 minutes.
Add chicken broth, chicken, corn, cumin and chili powder. Stir.
Taste and season with salt and pepper as needed.
Mix cornstarch and water then add to soup.
Bring soup to a boil, reduce heat and simmer 20 minutes while occasionally stirring.
Serve soup topped with tortilla strips, shredded cheese, avocado, cilantro and sour cream. Limes on the side.