Bring a large pot of salted water to a boil. Add the rotini pasta and cook according to package directions, about 8-10 minutes, until al dente. Drain and rinse under cold water.

In a large skillet, heat oil over medium-high heat. Add lean ground beef, breaking it up with a spatula. Cook for about 8-10 minutes until browned. Stir in taco seasoning and cool to room temperature.

In a large mixing bowl, combine cooled rotini, seasoned ground beef, chopped tomatoes, shredded cheddar, black beans, corn, and red onion. Toss gently to distribute evenly.

In a small bowl, whisk together French dressing and mayonnaise until smooth. Pour over the salad and toss gently to coat.

Right before serving, fold in the crushed Doritos for crunch. Serve chilled for best flavor.