See picture. Instead of one large cauliflower head it is producing individual florets. What is the possible reason for that? I have done the usual watering and fertilizing so don't think that is the issue.
Like cabbage's family plants, cauliflower has a growth phase followed by a flowering phase. It usually takes two seasons, with a winter in the middle.
It looks like this plant is on its second growth season.
So my guess is it got great stress ( drought or freeze) and started producing flowers too soon. It also could be one you planted the year before or something similar.
I doubt you can grow normal cauliflower from this. But in the end of summer you could harvest the seeds.
Cauliflower needs uninterrupted growth because interruptions can cause the plants to develop a head prematurely.
Usually the flowers stay small and open up in summer, when the night temperature doesn't drop significantly from the day temperature. However, from your profile I see you are in hardiness zone 10 in Northern hemisphere, so no way to have hot nights now.
In conclusion, if your watering and fertilizing were normal, and night temperatures were low, the only explanation is that the daytime temperatures were too high. You can read more about this on The Old Farmer's Almanac.