Sausage Cornbread Bake

1 pound bulk sausage
1 cup chopped onion
2 eggs
1 1/2 cups self-rising corn meal mix
1 (17 ounce) can cream-style corn
3/4 cup milk
1/4 cup vegetable oil
2 cups shredded sharp Cheddar cheese

Grease a 10-inch cast iron skillet or 2-quart baking dish. Saut