String Beans Vinaigrette

Ingredients

• 1 lb. fresh or frozen French-style green beans
• 1/2 medium onion, finely chopped
• 1 small garlic clove, minced
• 1/3 c. grated Parmesan cheese
• 8 oz. (small) Paul Newman's dressing
• 2 Tbsp. tarragon vinegar
• 1/2 tsp. salt
• 1/2 tsp. black pepper
• 4 plum tomatoes
• 1/2 c. black olives or more to taste