I have made this recipe before, at which time I didn't forget to buy an onion. Having eaten this curry with and without onion, I definitely suggest you add onion. I felt the original recipe did not have enough tomatoes, so I added more this time. Other ingredients that can be added to this Indian, Nepali, and Pakistani dish are peas, garlic, and ginger.
I used 2 teaspoons salt, 1 tablespoon extra virgin olive oil, 1 head cauliflower, 1 teaspoon ground cumin, 2 large potatoes, 4 tomatoes, and 2 teaspoons curry powder. Curry powder usually contains coriander, turmeric, cumin, fenugreek, and red pepper.
I boiled the 1/2 inch cubed potatoes in salted water for 4 minutes. I used russet potatoes. Russet potatoes have a high starch content, which makes them fall apart more easily once cooked. Yukon gold potatoes have less starch and more moisture. They hold their shape better than russet potatoes. You should avoid buying potatoes that have green spots.
I then added the 1 inch cauliflower florets and continued to boil for another 4 minutes.
While the cauliflower and potatoes were boiling, I heated the tablespoon of extra virgin olive oil. I added the cumin and cooked until fragrant and a little brown. This is where I should have added the diced onion. I would have cooked the diced onion for about 3 minutes.
Once the cumin was fragrant, I added my cubed tomatoes. I cooked the tomatoes for 3 minutes. About this time the potatoes and cauliflower florets were tender.
I drained the potatoes and cauliflower and added them to the tomatoes. I added 2 teaspoons of curry powder and probably 3 teaspoons of salt. I like salt. Once everything is thoroughly mixed, the dish is finished.
This is good, but don't forget the onion. It makes a noticeable difference in the flavor. I might add peas in the future. It was initially quite runny, but the potatoes must have absorbed some of the tomato juices.