In a medium sized pot, heat olive oil. Add onion and cook until fragrant. Stir in tomato paste. Add lentils and water, then bring to a boil, reduce heat, and simmer for 20 minutes while covered.
Meanwhile, prepare the sauce. Using a mortar and pestle or a food processor, grind garlic with a pinch of salt into a paste. Add in walnuts and continue to mash until it's a rough paste.
Transfer to a bowl, and stir in yogurt and parsley.
Once lentils are done cooking, drain remaining liquid. Mix lentils with yogurt sauce.
If using as a side dish, you can stop here.
If you want as more of an entree: In a large pan, heat a little olive oil and fry eggs. Top lentils with eggs, a little salt and pepper.
Recipe by Things I Made Today at https://www.thingsimadetoday.com/2014/01/29/nutty-garlicky-herby-lentils-fried-egg/