1
In a large pot, heat the oil over moderate heat.
2
Add the celery, onion, and carrot and cook, stirring occasionally, until the onion is translucent, 5 to 10 minutes.
3
Add the lentils, tomatoes, water, dried oregano, salt, and a pinch of freshly ground pepper. Bring to a simmer. Reduce the heat and cook, partially covered, until the lentils are tender, about 40 minutes.
4
Meanwhile, heat a large skillet over moderately high heat. Add the kielbasa and cook, turning, until browned, 3-5 minutes.
5
Stir the kielbasa into the lentils and simmer for 5 minutes. If the lentils are too thick for your taste, thin them with additional water.
