1/4 cup finely diced shallot
1/2 cup peeled and seeded cucumber, finely diced
2 tsp. kosher salt, divided
1 large English cucumber, roughly chopped (about 4 cups)
1/4 cup red wine vinegar
1/4 cup freshly squeezed lemon juice
1 Tbs. lemon zest
1 Tbs. freshly minced garlic
2 Tbs. chopped fresh dill, plus more for garnish
1/2 cup whole buttermilk
1½ cups sour cream or whole milk yogurt
1/4 tsp. freshly ground pepper
Cucumber slices, for garnish
Toss the diced shallot and cucumber with one teaspoon salt and let sit for 10 minutes.
In a blender or food processor, purée the chopped cucumber, vinegar, lemon juice, zest, and garlic. Reduce the speed to low and add the dill, buttermilk, sour cream, remaining salt, and pepper. Blend until incorporated.
Strain the diced cucumber and shallot mixture and add to the blender on low speed. If the soup is too thin, add sour cream to thicken. Adjust seasoning to taste. Divide among six bowls and garnish with cucumber slices and dill.