Sri Lankan Lentil Curry

I've had this recipe for years and can't remember where it came from! I'd written the name down as 'parapou' in my recipe book, but when I google 'Sri Lankan lentil curry' a bunch of recipes for 'parippu' appear. Whatever ...! Regardless of the spelling, this is quick, easy, and delicious on a chilly Canberra day.

2 cups orange lentils
1 tomato, chopped
3 or 4 cloves garlic
1 tsp mustard seeds
turmeric or saffron, to taste
red chillies, chopped
1 onion, chopped
coconut milk

Heat a little oil in a pan. Add onion and stir-fry for a minute. Add tomato and mustard seeds, stir until mustard seeds jump then add wet lentils. Add garlic and chillies. Cover with coconut milk and add turmeric/saffron. Simmer about 15 minutes, and serve with roti or rice.