Preheat the oven to 200°C. Spread the thinly sliced fennel over a baking sheet and toss with half of the olive oil. Roast the fennel in the oven for fifteen to twenty minutes until tender and lightly caramelized. Meanwhile, cook the quinoa in plenty of water according to package directions for ten to twelve minutes until cooked.
Heat the remaining olive oil in a frying pan over medium-high heat. Place the sea trout fillet skin-side down in the pan. Cook the fish for three to four minutes per side until cooked through.
Drain the quinoa once cooked. Finely chop the fresh dill. Mix the cooked quinoa with the dill, capers and lemon juice together well.
Divide the roasted fennel over a plate. Place the cooked sea trout directly on the fennel and spoon the prepared quinoa alongside.