Best black bean soup!

I first made this black bean soup when David had his wisdom teeth out and needed soft foods aplenty. The soup was easy to eat, not to mention delicious and filling. I'll eat this for lunch with a whole-grain roll, and be full until dinner time. Excelente!

Vegetarian black bean soup
Adapted from RecipeZaar

1 medium yellow onion, chopped
2 garlic cloves, minced
4 celery ribs, chopped (the celery is what makes it extra-delish, IMHO)
2 vegetable bouillon cubes
2 cups water
2 large cans black beans
1/2 tsp cumin
1 tbsp dried oregano
1/2 lemon, juiced
3 tbsp cornstarch

In a large pot, combine first five ingredients. Simmer until onions begin to turn translucent. Add black beans, cumin, and oregano, and cook for five minutes. Puree soup with immersion blender. In a small bowl, combine the cornstarch with three tbsp cold water. Add to pot, and stir well. Squeeze lemon into soup, and heat until thickened.