Preheat the Oven: Set oven to 350°F (175°C). Grease the baking dish lightly to prevent sticking.
Combine Wet Ingredients: Mix together whole kernel corn, cream-style corn, sour cream, and melted butter in a mixing bowl. Mix well until the ingredients are evenly incorporated.
Add Dry Ingredients: Gradually add the cornbread mix to the wet ingredients, stirring continuously. Ensure a smooth consistency without lumps. Add garlic powder, salt, and pepper to taste.
Layering in the Baking Dish: Pour half of the corn mixture into the greased baking dish. Sprinkle half of the shredded cheddar cheese evenly over the layer. Repeat with the remaining corn mixture and cheese.
Bake to Golden Perfection: Put the baking dish in the preheated oven. Bake for approximately 45-50 minutes or until the top is golden brown, and a toothpick inserted in the center comes out clean.
Serve and Enjoy: Allow the corn casserole to cool for a few minutes before serving. Cut into squares and serve warm.