How to Make It
Preheat oven to 350°F. Toss buckwheat with 1 tablespoon of the oil, ½ teaspoon of the salt, and several grinds black pepper on a rimmed baking sheet. Toast buckwheat until slightly darkened, 18 to 20 minutes, stirring buckwheat and rotating baking sheet halfway through. Let cool.
Toss together celery, apple, dill, vinegar, toasted buckwheat, ¼ cup of the pecorino, and remaining 2 tablespoons olive oil in a large bowl. Season with remaining ¼ teaspoon salt. Top with more dill and remaining ¼ cup pecorino.