Heat oil in a heavy pan over medium heat. Saute onion for 10 minutes or so, until it begins to turn golden. Add minced garlic and saute for another minute or so.
Add lentils and water to the saucepan. Bring mixture to a boil. Cover, lower heat, and simmer about 35 minutes, until lentils are soft ( this may take less time, depending on your water and the lentils).
Meanwhile cook the spinach in microwave according to package directions. Add spinach, salt and cumin to the saucepan. Cover and simmer until all is heated, about ten minutes. Grind in plenty of pepper and press in extra garlic to taste.