Method

soak and rinse the lentils, then soak in lukewarm water for 30 minutes (or use canned)
chop the onions and tomato, heat the olive oil in a large pan, then cook the onions and tomato for 4-5 minutes until soft.
Add the berbere spice (optional, chopped chillies if you want them), mix well into the onion mixture
add a cup of water to the mix and cook for about 10 minutes until the sauce reduces down (10 minutes)
add a cup of water to the mix and cook for about 10 minutes until the sauce reduces down (10 minutes)
add a cup of water to the mix and cook for about 10 minutes until the sauce reduces down (10 minutes) - not an error! repeating this step three times will give the lentils a rich layered flavour
Strain the lentils that have been soaking add 8 cups of water to the onion and tomato mix, and bring to the boil
Add the lentils, reduce the heat, cover and simmer, stirring occasionally. Cook for 25-30 minutes until the mixture is thick and the lentils are tender.