Cook the rotini pasta according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large mixing bowl, combine the cooled pasta, cherry tomatoes, corn, black beans, red onion, cilantro, and avocado.
In a small bowl, whisk together the lime juice, olive oil, garlic powder, cumin, salt, and pepper (and chili powder if using).
Pour the dressing over the pasta salad and toss gently to combine all ingredients.
Taste and adjust seasoning if necessary. Chill in the refrigerator for at least 30 minutes before serving to allow flavors to meld.