Cauliflower, tomatoes and feta are always a good combination. This being a winter frittata, I used canned tomatoes for the sauce, but in summer the same dish can be made with fresh tomatoes. Make sure to cook the sauce down until it is quite pasty. If it is too watery it will dilute the eggs and the texture of the frittata will be a bit watery. Even better, make the tomato sauce a day ahead and keep uncovered in the refrigerator.