1/4 to 1/2 cup raspberry vinegar or balsamic vinegar
1 Tbs. canola oil
Preheat oven to 375 degrees. Spread walnuts on baking sheet and toast in oven, stirring occasionally, until fragrant, about 7 minutes. Let cool.
In large bowl, combine watercress, beets, onion and toasted walnuts. Set aside.
Dressing: In small bowl, mix raspberry preserves, vinegar and oil until blended and smooth. Pour dressing over beet mixture, tossing to coat. Cover and let marinate at room temperature for 2 to 4 hours. Serve at room temperature.