Preheat oven to 375 degrees F (190 degrees C).
In a large skillet, brown ground beef over medium heat. Drain off any excess grease.
Add onion and garlic to the skillet and cook until softened, about 5 minutes.
Stir in chili powder, cumin, salt, and pepper. Cook for 1 minute more.
Stir in tomato sauce and diced tomatoes and green chilies. Bring to a simmer and cook for 5 minutes.
To assemble the Taco Ring, spray a 9-inch springform pan with cooking spray.
Arrange tortillas in a single layer on the bottom of the pan, overlapping slightly.
Spread half of the ground beef mixture over the tortillas.
Sprinkle with half of the shredded cheddar cheese.
Spread sour cream over the cheese.
Repeat layers of tortillas, ground beef mixture, cheese, and sour cream.
Bake for 20 minutes, or until cheese is melted and bubbly.
Let stand for 10 minutes before serving.
Top with your favorite taco toppings.