The classic recipe for this staple vegetable is to steam it and serve it with cheese sauce, or to serve it raw with veggies and dip, but cauliflower can do much more.
Try steaming or boiling the florets until they’re soft, then mash and serve mashed-potatoes style.
Or cut the crown vertically (top to stem) into inch-thick slices and grill them on the BBQ or in a pan.
Florets can be tossed with oil, seasonings (e.g. curry powder) and other cut vegetables, then wrapped in foil and baked or BBQed. (If you like to follow a proper recipe, try this one.)
The adventurous may want to experiment with cauliflower pizza crust: puree the florets, drain in a cheesecloth, then follow any promising recipe on the internet (such as this one).