- 1/2 cup plain whole-milk yogurt
- 2 tablespoons drained prepared horseradish
- 2 tablespoons chopped capers
- Finely grated zest of 1 lemon
- 1/4 cup plus 1 tablespoon extra- virgin olive oil
- 2 celery ribs, finely chopped
- 1 small onion, finely chopped
- 1 pound skinless, center-cut salmon fillet, cut into 1/4-inch dice
- 1/2 cup fresh bread crumbs
- 3 tablespoons chopped dill
- 1 large egg, lightly beaten
- 3/4 teaspoon kosher salt
- 1/4 teaspoon freshly ground pepper
- 4 kaiser rolls, split and lightly toasted
- In a small bowl, mix the yogurt with the horseradish, capers and half of the lemon zest.
- In a medium skillet, heat 2 tablespoons of the olive oil. Add the celery and onion and cook over moderately low heat until translucent, about 7 minutes. Transfer to a bowl and let cool. Add the salmon, bread crumbs, dill, egg, salt, pepper and the remaining lemon zest; mix gently and pat into 4 burgers.
- In a large skillet, heat the remaining 3 tablespoons of olive oil until shimmering. Add the burgers and cook over moderately high heat until browned outside and medium in the center, about 4 minutes per side.
- Spread the horseradish-dill sauce on both sides of the rolls. Add the burgers, close the sandwiches and serve.
The horseradish sauce and the uncooked burgers can be refrigerated separately overnight.