Microwave popcorn is often pre-seasoned with salt and other flavors, which can compete with the cheddar cheese flavor. Additionally, microwave popcorn can sometimes be greasy, which can make it harder for the cheese powder to stick to the popcorn. If you want to make cheddar cheese popcorn at home, it's best to start with plain, air-popped popcorn or popcorn that has been popped on the stovetop using oil. This will give you a neutral base to which you can add the cheddar cheese powder and other seasonings.