From: foodtv.com

Ingredients
1/4 cup balsamic vinegar
1/4 cup soy sauce
4 portobello mushrooms, cleaned, gills removed, quartered, and cut into slices 1/8 to 1/4-inch thick
1 red onion, diced
1 cup baby spinach (packed), soaked to remove grit, well rinsed and dried in a salad spinner or with paper towels
2 large ripe fresh tomatoes
1 tablespoon fresh dill, minced
Directions
Heat balsamic and soy in a skillet and allow mushrooms to poach while the sauce reduces. Remove from heat and let cool. In a mixing bowl toss with onion, spinach and tomatoes. Serve chilled, family style, garnishing with fresh dill.