Pull off the cauliflower leaves; discard them. Remove the cauliflower's core; discard it. Cut the cauliflower head into small florets, about 1 1/2 inches.
In a large casserole dish, heat the oil over medium heat.
Add the onions; cook for 5 minutes, stirring frequently.
Add the garlic; cook for 1 minute.
Add the cauliflower, bay leaves, red pepper flakes, and salt. Cook for 5 minutes, stirring occasionally.
Add the undrained tomatoes and the water. Simmer, covered, for about 20 minutes; stir occasionally. If the dish seems watery, increase the heat to medium. Cook uncovered till the liquid has been reduced, for up to 15 minutes more.
Sprinkle it with the cheese.
Serve hot either over pasta, or as a side dish on its own.