Heat the oil in a large skillet or sauté pan over medium heat.

Add the chopped onion and cook until softened.

Stir in the crushed garlic and grated ginger, then cook briefly until fragrant.

Add the garam masala or curry powder, cumin, turmeric, salt, and pepper. Stir well so the spices bloom.

Pour in the tomato sauce, water, and coconut milk, then stir to combine.

Add the dried green lentils and mix well.

Bring to a gentle simmer and cook until the lentils are tender and the curry has thickened, stirring occasionally.

Stir in the chopped coriander leaves if using.

Serve hot with cooked rice.