Boil pasta in salted water until al dente. Drain and set aside.
Cook ground beef in a skillet over medium heat until browned. Drain excess fat. Stir in taco seasoning and a splash of water. Simmer for a few minutes.
In a bowl, mix sour cream, cream cheese, and diced tomatoes until smooth. Add the beef mixture and stir until well combined.
Preheat oven to 375°F (190°C). Layer half of the pasta in a 9x13 inch baking dish, followed by half the meat mixture. Repeat layers. Top with shredded cheddar cheese and green onions.
Bake for 20 minutes, removing foil in last 10 minutes to melt cheese. Serve hot.
Notes
Leftovers can be stored in the fridge for up to 3 days. Reheat in the oven to retain its delightful texture.