How to Make It
Preheat the oven to 425°. In a food processor, pulse the carrots until finely chopped. Add 1/2 cup of the parsley and the dill and pulse until minced. Scrape the tabbouleh into a bowl. Stir in 1 tablespoon each of oil and lemon juice; season with salt.
Wipe out the processor. Add the garlic and walnuts; pulse until chopped. Add the tahini, jalapeño, cilantro, cumin, coriander, 1/4 cup of the oil and the remaining 1/2 cup of parsley and 2 tablespoons of lemon juice. Pulse until smooth. Scrape into a bowl; season with salt.
Arrange the fish in a medium baking dish. Drizzle with the remaining 2 tablespoons of oil, season with salt and turn to coat. Roast for 8 to 10 minutes, until the fish is cooked through. Transfer to plates. Spread some of the walnut tahini on the fillets and spoon the carrot tabbouleh alongside. Serve the remaining tahini at the table.