Tomato Salad With Basil-Buttermilk Dressing
["2 c. packed fresh basil leaves (about 2 large bunches)", "3/4 c. buttermilk", "2 green onions, thinly sliced", "3/4 tsp. salt", "3/4 c. mayonnaise", "1/2 tsp. pepper", "4 lb. firm ripe tomatoes", "fresh basil sprigs"]
["Blend 2 cups fresh basil, buttermilk, sliced green onions and salt in processor until smooth.", "Transfer to bowl.", "Add mayonnaise and pepper. Whisk until dressing is smooth. Let stand 30 minutes. Season to taste with salt and pepper.", "(Can be made 8 hours ahead. Cover tightly and refrigerate.)"]
["basil", "buttermilk", "green onions", "salt", "mayonnaise", "pepper", "firm ripe tomatoes", "fresh basil sprigs"]