Make the dressing by blending together Greek yogurt, lime juice, cilantro stems and leaves, garlic, salt, and cayenne until smooth. Refrigerate while preparing the salad.

Cook the pasta in salted boiling water according to package directions (about 8–10 minutes for al dente). Drain and rinse with cold water.

Boil water for the corn; cook for 1½–2 minutes until tender. Drain and cool under cold water. Chop the cherry tomatoes, red onion, and cilantro.

In a large bowl, mix cooled pasta, sweet corn, cherry tomatoes, red onion, and cilantro. Drizzle in dressing and toss until well-coated.

Before serving, fold in diced avocado and sprinkle with Cotija cheese if desired. Serve immediately.