Preheat oven to 350°F. Spray a 9x13-inch baking dish with cooking spray.
In a large skillet over medium-high heat, add ground beef and onion. Cook until beef is no longer pink and onion is softened, about 5-7 minutes. Drain excess fat.
Meanwhile, cook rotini pasta according to package directions until al dente. Drain and set aside.
Add garlic and cook for 1 minute more.
Stir in taco seasoning, Rotel tomatoes, tomato sauce, and beef broth. Bring to a simmer and cook for 5 minutes.
Remove from heat and stir in sour cream until fully combined.
Add the cooked pasta and mix until evenly coated.
Transfer the mixture to the prepared baking dish. Top with all of the cheese.
Bake uncovered for 20-25 minutes until hot and bubbly and cheese is melted.
Let stand 5 minutes, then sprinkle with green onions before serving.
Notes
*Use 2 cups of your favorite salsa in place of the Rotel®.