Put the lentils in a small sauce pot and pour in 4 cups water. Cover and bring to a boil. Once boiling, lower heat and simmer for about 20 minutes, until lentils are soft. Drain and set aside.
About 10 minutes before the lentils are done boiling, preheat a medium soup pot over medium heat. Saute the onion in water (small amount) for about 7 minutes, until softened. Add the garlic and saute a minute more.
Add the cooked lentils, the chili powder, and oregano, and mix. Add the tomato sauce and tomato paste. Cook for about 10 minutes.
Turn the heat off and let sit for about 10 minutes, so that the flavors can meld, or go ahead and eat immediately if you can't wait.