Heat 2 tablespoons of vegetable oil in a kadai or deep saucepan over medium heat. Add 1 teaspoon of cumin seeds. Let them sizzle and turn fragrant, which should take about 30 seconds.

Add the finely chopped onion to the pan. Cook on medium heat, stirring occasionally, until they turn a deep golden-brown color. This takes about 6 minutes and is crucial for the gravy's flavor base.

Stir in 1 tablespoon of ginger-garlic paste. Cook for about 1 minute, stirring constantly to prevent it from sticking to the bottom, until the raw aroma disappears.

Add the chopped or pureed tomatoes, 1/2 teaspoon of turmeric powder, 1 teaspoon of Kashmiri red chili powder, 1 teaspoon of coriander powder, and 1 teaspoon of salt. Cook this mixture on medium heat for 5 minutes, stirring frequently, until the tomatoes soften completely and you see tiny droplets of oil separating at the edges.

Add the cubed potatoes and toss them in the spiced tomato mixture for 1 minute so they are well coated. Pour in 1 1/2 cups of water and stir well.

Bring the liquid to a boil, then reduce the heat to low-medium. Cover the pan with a lid and simmer for 8 minutes, or until the potatoes are almost cooked through and can be easily pierced with a fork.

Stir in 1 cup of green peas and 1/2 teaspoon of garam masala. Cover the pan again and cook for an additional 3 minutes until the peas are tender and hot.

Turn off the heat. Stir in 2 tablespoons of freshly chopped coriander leaves. Let the curry rest covered for 2 minutes before serving so the flavors settle.