Cut turkey tenderloin lengthwise into quarters. In a skillet, cook the turkey, onion and garlic in butter until turkey is no longer pink and vegetables are crisp-tender. Remove turkey and let stand until cool enough to handle. Cut into cubes. Transfer vegetables to a saucepan. Add the turkey, broth, beans, tomatoes, salsa, parsley and cayenne. Bring to a boil. Reduce heat; simmer, uncovered, for 12-16 minutes or until slightly thickened. Top each serving with cheese or sour cream if desired.