Southwest Cornbread Layered Salad

1 (6-8 ounce) package cornbread mix, cooked according to package instructions and cooled (or your favorite recipe of cornbread)
2 cups mayonnaise
3 teaspoons Mexican chili powder or mild chili powder
1/2 teaspoon salt
2-3 tablespoons freshly chopped cilantro, optional
1/2 head torn iceberg lettuce or 2 heads Romaine lettuce chopped (or you can substitute a bag of torn lettuce)
1 (14-ounce) can shoepeg or yellow corn, drained
1 (14-ounce) can black beans, rinsed and drained
6 Roma tomatoes, chopped
1/2-3/4 cup finely chopped red onion
2 cups shredded cheese (Colby jack, Mexican blend, cheddar, etc.)

Crumble cornbread into fine crumbs; set aside. Stir together the mayonnaise, chili powder, salt, and chopped cilantro, if desired. In a 4-quart glass bowl or trifle dish, place half of the lettuce, then sprinkle with half of the cornbread crumbs. Spread half of the mayonnaise mixture on the cornbread layer. Layer half each of the corn, black beans, tomatoes, onions, and cheese. Repeat layers with remaining ingredients. Refrigerate for 2 hours before serving.