Refreshing Watermelon-Tomato Salad

REFRESHING WATERMELON-TOMATO SALAD1 c. thinly sliced red onion2 T. white vinegar1 T. vegetable oil1 t. sugarKosher salt, black pepper1 (8-oz.) log goat cheese, softened2 T. milk3 T. chopped fresh dill, dividedZest of 1 lemonJuice of 1 lemon4 c. thinly sliced…