Place lentils and chopped onions in water, bring to a boil; reduce heat, cover and simmer for 1 hour.

 

Mix oil, flour, cumin, salt, and pepper in bowl. Add 1/4 cup of hot soup; stir well. Pour mixture back into soup and let simmer until lentils are tender. Add lemon juice and simmer 5 more minutes.

 

Garnish with lemon.