3/4 ts Salt 2 c Fresh basil leaves; packed 3/4 c Buttermilk 2 Green onions; thinly sliced 3/4 c Mayonaise 1/2 ts Pepper 4 lb Firm ripe tomatoes Blend basil, buttermilk, green onions and salt in processor until smooth. Transfer to bowl. Add mayonnaise and pepper and whisk until dressing is smooth. Let stand 30 minutes. Season to taste with salt and pepper. Core and slice tomatoes. Arrange on platter. Spoon dressing over to coat. Garnish with basil leaves.