As I see you haven't had any replies yet, you can have my simple recipe. Quantities are not given as tastes vary & some people like a lot of lentils while others like just a few, adjust to suit yourself. This is written in idiotproof format because I don't know how much cooking experience you have.
Notes - If you are in a hurry or like a very mild flavour, use canned lentils or split red lentils. Brown or Puy Lentils take longer, but give a stronger, earthier flavour - experiment to see which you like best.
Basic ingredients:
Lentils
Tomatoes - Fresh, Canned, Tomato puree, Passata - mix & match which you prefer. Oven Roasted toms add extra flavour, as do sundried tomatoes.
Onions
Garlic
Celery
Veg stock - fresh or granules - Kallo stock is good
Veg Oil
Optional extras:
Carrots
Potatoes
Parsnips
Coriander - Fresh leaves or freshly ground seeds
Smoked Paprika
Chilli
Fresh Parsley or basil
Summer or winter Savoury (Herb reputed to make pulses more easily digestible & less errr, windy)
Rosemary or Sage
Fresh black Pepper
Turkish Lentil soup - Once basic soup has cooked allow to cool slightly, then add lots of fresh mint, some yoghurt, fromage frais or single cream and a little chilli. Blend until reasonably smooth and serve with wedges of lemon. Unusual but delicious.
Method:
Finely chop onion, celery and garlic, setting celery and garlic aside. Heat small amount of oil in saucepan & add onion, after 5 min add celery and onion, fry until garlic aroma fills the room, don't allow garlic to burn. Add pureed or finely chopped tomatoes and any other veg (if using), and add stock and lentils. Remember that lentils absorb a lot of water during cooking, roughly a handful of dry lentils to 2 cups of water/stock should be ok, but check after soup has cooked for 15 min to see if more water is needed. Lentil soup tastes best if allowed to cook slowly over a moderate heat, but if you don't have the time split red lentil soup takes 20 - 30 min to cook, and brown / puy lentil takes about 45 - 55 min.
Hope this helps
Lisa