Soak the cedar plank in water for at least 1 hour.
Finely grate enough zest from the oranges and the limes to make 1-½ teaspoons of each; set aside. Squeeze 1 cup juice from the oranges and ⅓ cup juice from the limes. In a small saucepan over medium-high heat, combine the orange juice, lime juice, lemon juice, and honey and bring to a boil. Continue to boil until the liquid is reduced to ¾ cup, 10 to 14 minutes. Remove from the heat. Stir in the butter, the orange zest, lime zest, and 1-½ teaspoons of the coriander. Let the glaze cool slightly. Stir in the cilantro.
Place the salmon fillet on a large baking sheet. Cut the fillet into six individual portions, cutting right down to the skin but not through it.
In a small bowl combine 1 tablespoon of the remaining coriander, the salt, cumin, and pepper. Pour ½ cup of the citrus glaze slowly and evenly over the top of the salmon, reserving the remaining glaze for serving. Spread the glaze evenly over the salmon, brushing some glaze between the individual portions. Season the salmon evenly with the spice mixture. Allow the salmon to marinate at a cool room temperature for 45 minutes, basting occasionally with any glaze that runs onto the baking sheet.
Meanwhile, make the salad: In a small bowl whisk the oil, orange juice, vinegar, salt, pepper, and the remaining 1-½ teaspoons coriander until well blended and emulsified. Stir in the cilantro and reserve at room temperature. In a large bowl combine the frisée, onion, dates, and tangerines. Refrigerate, covered, until ready to serve.
Prepare the grill for direct and indirect cooking over medium heat (350° to 450°F).
Brush the cooking grates clean. Remove the soaked plank from the water and place it on the cooking grate over direct medium heat. Close the lid. After 5 to 10 minutes, when the plank begins to smoke and char, turn the plank over and place it over indirect medium heat. Put the salmon on the plank, skin side down, and cook, with the lid closed, until the salmon is just opaque in the center and begins to brown slightly around the edges, 25 to 35 minutes. Transfer the plank with the salmon to a heatproof surface. Slide a spatula between the skin and flesh and transfer to serving plates. Spoon some of the remaining citrus glaze over each serving. Gently toss the salad with the dressing and serve it alongside the salmon.