Remove green leaves and a part of the stem so the cauliflower will still stay together and sit flat when upright. Place cauliflower upside down (so it doesn't float so much) into large pot and cover with cold water and about 1 tablespoon salt.
Bring to boil and simmer 30-40 minutes or until the cauliflower stems are tender, but before the cauliflower starts to fall apart. Remove from heat and carefully remove from pot using a large slotted spoon.
Place right side up into baking dish. Sprinkle with salt and pepper.
Slather the cream of mushroom soup over the entire head of cauliflower evenly. Top with cheese* and bake at 350 for 20-30 minutes or until hot and bubbly.*If you want to make this ahead, cover and refrigerate before you bake. On the day you are ready to serve, remove from fridge and bake at 350 for 30-40 minutes or until hot and bubbly.