Put the cauliflower florets in a steamer and cook until soft, about 12 minutes.
Meanwhile, warm the butter in a pan, add the tomatoes and sauté until mushy.
Remove from the heat and add the cheese, stirring until melted.
Mix the cauliflower with the tomato and cheese sauce, then blend to the desired consistency.
Variation:
Steam the cauliflower until soft, then blend it with 3 tablespoons of cheese sauce, omitting the seasoning from the sauce.