Preheat oven to 350°F. Toast hazelnuts on a rimmed baking sheet, tossing occasionally, until golden brown, 13–15 minutes. Wrap nuts in a kitchen towel and let steam 1 minute. Rub nuts in towel to remove loose skins (don't worry about skins that don't come off) and let cool.
Meanwhile, whisk vinegar, orange juice, and 2 tsp. salt in a medium bowl, then whisk in 3 Tbsp. oil in a slow, steady stream.
Coarsely chop cooled nuts. Toss with remaining 1 1/2 tsp. oil and a pinch of salt in a large wide bowl. Core and thinly slice apples; add to bowl along with endive and radishes.
Drizzle dressing over salad. Gently but thoroughly toss just until salad is evenly dressed; adjust seasonings. Divide salad among serving plates. Top with cheese and pomegranate seeds.
Nuts can be toasted and cooled up to 3 days ahead. Keep covered at room temperature.
