Peel and finely chop the onion. Peel garlic and chop finely. Heat the oil in a pot, fry the onion and garlic. Add lentils and sprinkle with curry. Stir in tomato paste and add stock.
Simmer the lentils at medium heat for about 10 minutes. Season with salt, pepper and curry. Stir several times. Cook spaghetti in boiling salted water for about 8 minutes. In the meantime wash parsley, dab dry and chop finely.
Drain the spaghetti and arrange on a plate with the lentil curry. Sprinkle with parsley and garnish with parsley as desired.