Brush the corn with oil and season with ½ teaspoon salt and ¼ teaspoon pepper. Lay on a sheet pan.
Broil the corn for 15 minutes, rotating frequently, until all sides are charred. Let cool for 15 minutes.
While the corn is cooking, add the pasta to a pot of boiling water and cook according to package directions.
In a small bowl, combine the sour cream, mayonnaise, lime juice, chili powder, the remaining salt, the remaining pepper, and the cayenne pepper. Set aside.
Drain the pasta in a colander and rinse under cold water.
Remove the corn from the cob with a sharp knife, working in a large bowl that you plan to serve the salad in.
Add the cooked pasta to the bowl with the green onions, cilantro, red pepper, and cotija cheese.