Heat oil in a large sauce pan over medium high heat; add the mustard and cumin seeds. Once the seeds start to pop, add the cauliflower and cook till the florets are lightly browned, about 2~4 minutes.
Add the garlic and cook for about 1 minute or until garlic is cooked through and smells fragrant.
Stir in the coconut milk and bring to a boil. Add salt, pepper and curry leaves.
Reduce the heat to medium-low, cover and cook till cauliflower is tender, about 8~10 minutes.
Add the spinach into the pan and cook till the leaves have wilted, about 5~6 minutes.
Add the tomato and cook till the tomato is tender, about 3~5 minutes. Serve with rice or roti.