"This no-fuss dish also works great as an appetizer on slices of toasted crusty bread."
1. In a small bowl, mix juice, mustard and garlic. Add oil in a thin stream, whisking constantly. Taste and season with pepper.
2. Mix beans, tuna, tomato, onion and parsley in a large bowl. Add dressing and toss to coat. Taste and adjust seasoning. Serve over mixed greens, if desired.