2 1⁄2 lb. firm, thick fish fillets such as swordfish, striped bass, or halibut, cut into 1-by-2-inch cubes
1⁄2 cup extra-virgin olive oil
Juice of 3 lemons (½ cup)
1 tbsp. fresh dill, finely chopped
Arugula, grilled fresh pineapple rings, and lemon slices, for serving (optional)
Vegetable oil, for brushing
40 red or yellow cherry tomatoes
In a large bowl, combine the cilantro, garlic, coriander, cumin, salt, pepper, and fennel seed, if using. Add the fish and toss to coat. Let rest for 10 minutes.
In a separate medium bowl, whisk the olive oil, lemon juice, and dill. Pour the mixture over the fish, turning to coat. Cover and refrigerate for 1 hour.
If using wooden or bamboo skewers, submerge ten 12-inch skewers in cold water; let soak for at least 30 minutes. Line a platter with arugula or grilled pineapple rings if desired; set aside.
Heat a grill or grill pan to medium heat, and brush lightly with vegetable oil. Or, preheat the broiler and brush a baking sheet with vegetable oil. Thread about 5 pieces of fish onto each skewer, adding a cherry tomato lengthwise between each piece.
Transfer the kebabs to the grill or under the broiler, spacing them at least 2 inches apart; cook until the fish is just cooked through, 6–8 minutes. Remove and transfer to the prepared platter. Serve immediately with the lemon slices, if using.