In a large pot, heat the oil until shimmering. Add the onion, garlic, coriander, cumin, 2 teaspoons salt and 1 teaspoon pepper, then cook, stirring, until the onion is translucent. Stir in the tomato puree, beans and 1 cup water, then bring to a simmer. Simmer, uncovered and stirring occasionally, for 15 minutes. Season with salt and pepper.