Brown the Beef: In a large skillet over medium-high heat, add the 1 pound ground beef and cook for 5-7 minutes, breaking it apart with a spoon as it cooks, until it's no longer pink and has developed a light brown crust.
Add Taco Seasoning: Sprinkle the 1 ounce taco seasoning over the cooked beef, add 1/4 cup water, and stir well to combine, cooking for another 1-2 minutes until the sauce thickens slightly.
Cool the Beef: Transfer the seasoned ground beef to a plate and let it cool to room temperature before adding it to the pasta, about 5 minutes.
Boil the Pasta: Bring a large pot of salted water to a boil, add the 16 ounces rotini pasta, and cook according to package directions until al dente, usually 8-10 minutes, then drain and rinse with cold water to stop the cooking process and cool it completely before mixing.
Combine Base Ingredients: In a very large bowl, add the cooled pasta, cooled ground beef, halved cherry tomatoes, sliced green onions, shredded cheddar cheese, and shredded Monterey Jack cheese, and toss gently to combine.
Add the Dressing: Pour the 1 cup Catalina dressing over the mixture and toss everything together until every ingredient is evenly coated.
Fold in Doritos: Gently fold in 1.5 cups of the crushed nacho cheese Doritos, reserving the remaining 0.5 cups for topping to keep them crunchier longer.
Garnish and Serve: Top with the reserved crushed Doritos, sprinkle the fresh cilantro over the top, and serve immediately or refrigerate until ready to serve.