Heat oil in a large pot on a medium heat. Cook onions, garlic and ginger until soft.
Add spices and salt and cook for a further 1 minute, or until fragrant.
Rinse lentils under cold water, drain and add to pan. Stir lentils to coat with spiced onion mixture. Add tomatoes and water/stock and mix well.
Leave uncovered and cook over a low heat for about 20 minutes, or until the lentils are cooked through.
Remove from the heat and add a few spoonful’s of the dahl to a bowl. Whisk in yogurt and then combine mixture to the remaining dahl until fully combined; this will ensure the yogurt does not separate.
Serve with a side of poppadum and a sprinkle of black sesame seeds and coriander.