In a medium skillet, heat over medium-high heat, then add the lean ground beef. Cook for about 6-8 minutes, breaking it apart until browned. Drain excess grease and set aside.

Bring a large pot of salted water to a boil, add rotini pasta, cooking according to package instructions for about 8-10 minutes. Drain and rinse with cold water.

In a large mixing bowl, combine cooked ground beef, cooled rotini pasta, taco seasoning, diced yellow sweet pepper, diced white onion, halved grape tomatoes, shredded cheddar cheese, and shredded iceberg lettuce. Fold gently.

Drizzle with French dressing and sour cream, about ½ cup each. Toss gently to coat without crushing pasta.

Serve immediately in large bowl or plates, sprinkling crushed Doritos on top. Save Doritos until serving if preparing ahead.