INGREDIENTS
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1 pound ground beef (10 to 20% fat)
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1 yellow onion, diced
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1 tablespoon dried oregano
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1 tablespoon Worcestershire sauce
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1 tablespoon red wine vinegar
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1 (6-ounce) can tomato paste
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1 1/2 cups tomato sauce
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1/4 teaspoon salt
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4 whole-wheat hamburger buns