Heat up oil in a deep dish pan. Preferably, use olive oil, but refine oil can also work. Add chopped garlic in it once the oil heats up.

Add finely diced onions and salt. Cook till they are soft and mushy. Remember to not burn them and cook on a medium to low flame.

Take some fresh tomatoes and cook them in hot water for about 10 minutes. Once they are soft, peel the skin off and mash them properly.

Add the mashed tomatoes to the pan with garlic and onions and add any extra seasonings like basil or pepper. Cook on a low flame for 25-30 mins.

Once the sauce is cooked, remove it from the heat and let it cool down. After complete cooling, transfer the sauce into a clean, dry glass jar and store it for use.