Take a pan, add potatoes, salt, red chilli flakes, turmeric powder, kalonji and water. Mix it well and cover the lid. Cook it in medium flame.

When potatoes become tender, add lemon juice (you can change the quantity of lemon juice according to your taste buds). Mix it well.

Dissolve cornflour in a bowl, then add into potatoes mixture. Whisk it continuously while adding cornflour. Consistency of Tarkari should be medium. Cook it for a minute in low flame.