Ingredients

• 2 tablespoons low-fat mayonnaise
• 2 tablespoons nonfat sour cream, or nonfat plain yogurt
• 1 teaspoon lemon juice
• 1 tablespoon extra-virgin olive oil
• 2 4-ounce portobello mushrooms, stems removed, caps sliced ½ inch thick
• ⅛ teaspoon salt
• Freshly ground pepper, to taste
• 8 slices sourdough bread
• 1 clove garlic, halved
• 1 cup loosely packed basil leaves, torn into shreds (if large)
• 2 tomatoes, sliced