Step 1

Toast ¼ cup raw walnuts (if using) in a dry small skillet over medium heat, tossing often, until fragrant and slightly darkened, about 5 minutes. Coarsely chop; set aside.

Step 2

Pat four 4–6-oz. skin-on salmon fillets dry with paper towels and season all over with kosher salt. Arrange fillets skin side down in a cold large cast-iron skillet. Place pan over medium heat and cook salmon, undisturbed, until skin is crisp and deeply browned and flesh is opaque halfway up sides, about 5 minutes. Turn fillets over and cook just until opaque throughout, about 4 minutes. Stand fillets on their sides and cook until lightly browned, about 30 seconds per side.

Step 3

Meanwhile, whisk 2 garlic cloves, finely grated, 3 Tbsp. tahini, and 1 Tbsp. fresh lemon juice in a medium bowl. Add ¾ cup plain whole-milk Greek yogurt and whisk to combine; season with salt.

Step 4

Whisk 2 tsp. finely grated lemon zest, ¼ cup extra-virgin olive oil, and remaining 3 Tbsp. fresh lemon juice in another medium bowl; season with salt and freshly ground pepper. Add 1 large fennel bulb, thinly sliced, ½ cup coarsely chopped dill, ⅓ cup dates, pitted, coarsely chopped, ¼ cup Castelvetrano olives, smashed, pitted, and reserved walnuts and toss to coat.

Step 5

Spread yogurt sauce on plates and place salmon on top. Arrange salad around; top with fennel fronds.