Neely's Chicken Salad in Tomato Cups

INGREDIENTS

• 1 celery rib, chopped
• 3/4 cup mayonnaise
• 1 head butter lettuce
• 1 cup slivered almonds
• 2 tablespoons white wine vinegar
• 6 large beefsteak tomatoes
• 1/2 small red onion, diced
• Kosher salt and freshly ground black pepper
• 3 cups halved seedless red grapes
• 1 shallot, chopped
• 1 rotisserie chicken, skinless and meat shredded or diced
• 2 tablespoons freshly chopped tarragon leaves