This is a simple soup, made in a few minutes.
In a small skillet over medium heat, cook onions in butter and oil until tender.
Meanwhile, in a medium saucepan, bring water to a boil Pour beans and tomatoes into water. Stir cooked onions into mixture and simmer 5 minutes. Puree with the pepper sauce and ketchup in a blender or food processor, or using an immersion blender. Return to heat, season with salt and pepper, and heat through.
Per Serving: 224 calories; protein 6.7g; carbohydrates 32.6g; fat 9.8g; cholesterol 15.3mg; sodium 578.4mg.