There is no need to add additional water to this recipe as the onions and tomatoes release enough water.
If it’s not tomato season, use canned diced tomatoes (the whole contents of the can) for the best flavor.
If using fresh tomatoes, I suggest using roma tomatoes because they have less water content compared to other tomatoes. This results in a thicker masala. If using different tomatoes, you will likely need to boil off water at the end.
Make sure to adjust the temperature to sauté at the highest setting when sautéing the onions. It is up to you as to how brown you would like the onions. I have skipped fully browning them before and the masala still turns out well. The more caramelized the onions, the sweeter the masala will be.
You can also make this masala without the ginger, garlic and spices if you prefer. Just be sure to keep that in mind when preparing meals.
Learn how to store this masala by reading this blog post. You will want to make sure the onion masala is cold before putting it in the freezer. I store it in the fridge first, then once it’s cold I put it in the freezer. This helps to reduce freezer burn.