A brilliant twist on traditional fajitas, this weeknight-friendly soup is sure to become a family favorite. Partially freeze the beef for about 30 minutes for easier slicing into strips.
In a medium-sized bowl, combine the garlic powder, cumin, paprika, and cayenne. Add the steak strips and toss to coat. Coat a 4-quart nonstick Dutch oven with cooking spray and place over medium-high heat. Add the steak strips, half at a time and cook until brown, stirring occasionally, for 2-4 minutes. Remove the meat from the pan.
Heat the oil in a Dutch oven over medium heat. Add the sweet peppers and onion and cook until lightly browned and just tender, stirring occasionally, for 5 minutes. Add the broth and undrained tomatoes. Bring to a boil. Stir in the steak strips and heat through.
Add a dollop of sour cream to each serving and top with lime zest and tortilla chips. If desired, top with avocado and cilantro.