Using a spoon, hollow out the top 1/4 inch of tomato halves. Top each tomato half with 1 teaspoon of pesto sauce and an onion slice. Arrange tomatoes in 2 foil pie plates.
In a covered grill place the foil pans containing the tomatoes in the center of the grill rack, but not directly over the coals. Cover and grill for 10 to 15 minutes or until the tomato halves are heated through.
In a small mixing bowl stir together cheese, almonds and snipped parsley. Sprinkle over tomatoes. Cover and grill about 5 minutes more or until cheese is melted. Season to taste with salt and pepper. If desired, garnish with fresh parsley sprigs. Makes 6 servings. Enjoy!