Preheat the oven to 350°F and coat a medium casserole dish or 9X13 baking dish with cooking spray. Set aside.
In a large cast iron skillet over medium-high heat, brown the 1 1/2 pounds ground beef. If using stainless steel, add 1 teaspoon vegetable oil to prevent sticking. IF the beef has a lot of fat or liquid evaporating, drain it off as you go.
Add the chopped 1/2 cup white onion and minced 3 cloves fresh garlic, continuing to cook until the onion starts to soften.
Add the drained 10 ounces diced tomatoes with green chiles, 3/4 cup low-sodium beef broth, chopped 1/2 cup cilantro and 1 tablespoon taco seasoning. Toss to coat and heat, approximately 3 minutes.
Add the 1/2 cup sour cream and 1/2 cup of the shredded cheese. Mix and then remove from heat to allow mixture to thicken.
Coarsely crumble half of the tortilla chips with your hands, place in the bottom of the casserole dish. Top with half of the browned beef mixture and then half of the remaining shredded cheese. Repeat these layers once more.
Bake in the oven, uncovered, for 20 minutes.
Remove and allow to cool for 5 minutes before cutting to serve and topping with desired toppings.
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