Spray a large stockpot with the vegetable oil.
Add the olive oil and heat over medium-high heat.
Add the onion to the hot oil and saute until golden brown (about 4 minutes).
Add the lentils, broth, and water to the pan and stir. Bring to a boil over high heat, then reduce heat and simmer, covered, for 45 minutes or until lentils are soft. Stir occasionally.
Add the spinach, pepper, and allspice. Stir, then simmer, covered, for 15 minutes.
Thin the soup with additional water or broth if necessary.
Pour the soup into soup bowls and top with the grated cheese.