In a bowl, combine the mayonnaise, sour cream, minced onion, chili powder, garlic powder, and salt.
Pour the mayonnaise mixture over the corn and mix until well combined.
Bake at 400℉ for 30 minutes until bubbly throughout and golden brown around the edges and on top. Give the casserole a stir midway through cooking to prevent scorching around the edges.
Serve topped with cilantro and queso fresco cheese.
Notes
I cook this in a convection oven that cooks food very quickly. So, I regularly give the corn a toss as it cooks, to prevent too much scorching around the top and sides. In a regular oven, this isn't necessary.
I don't bother to thaw the corn before assembling. Corn thaws quickly, so you do not need it completely thawed before assembling regardless.
A serving size of corn is 2/3 cup. I purchase 32 oz bags unless I can get to Walmart and get 100 oz bags..