Pour 2-3 teaspoon cooking oil of choice into a pan on low heat. Add sliced onions. Increase stove heat to medium gradually to cook the onions until golden brown.
Add tomatoes and turn down heat gradually; add little bit of water to get the two to mix well in pan and avoid sticking to pan.
While adding fresh tomatoes to pan also add pinch of turmeric powder and curry paste or powder. It helps to add spices to vegetables during cooking, so that the spices don't taste raw while eating and vegetables absorb the flavour. Turn off heat after the tomatoes are soft and cooked; add chopped coriander.