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In a 3- to 4-quart pan over medium-high heat, cook onion and garlic in olive oil, stirring often, until onion is limp and starting to brown, 6 to 8 minutes.

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Add beans, tomatoes and their juice, cumin, and 1/2 cup water; bring to a boil, then reduce heat and simmer, stirring occasionally, to blend flavors, about 15 minutes.

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Stir in cilantro, chipotle puree, and rice vinegar.

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Add salt to taste.

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Spoon chili equally into four bowls and top each with 1 tablespoon sour cream and, if desired, with tomato, salsa to taste.