Heat olive oil in a large skillet over medium-high heat. Add ground beef and cook for 8 to 10 minutes, breaking it apart with a wooden spoon until completely browned. Drain excess grease.

Add chopped onion to the skillet and cook for 5 minutes until softened. Stir in minced garlic and cook for 1 minute until fragrant.

Pour in diced tomatoes with juices, tomato sauce, taco seasoning, chili powder, cumin, and cayenne pepper if using. Season with salt and pepper. Reduce heat to medium-low and simmer for 10 to 15 minutes, stirring occasionally until sauce thickens slightly.

While sauce simmers, bring a large pot of generously salted water to a boil. Cook elbow macaroni according to package directions until al dente, about 7 to 8 minutes. Drain well and set aside.

Preheat oven to 350°F. In a large mixing bowl, combine cooked pasta with taco meat sauce. Stir in sour cream and 3 cups of cheddar cheese until evenly distributed and cheese starts to melt.

Transfer mixture to a greased 9x13 inch baking dish. Top with remaining 1 cup cheddar cheese and 1 cup Monterey Jack cheese.

Bake uncovered for 20 to 25 minutes until cheese is melted and bubbly. Let rest for 5 minutes before serving. Garnish with fresh cilantro if desired.