How to Make It
Preheat the oven to 375º. Cut off the beet greens. Discard the stems and tear the leaves. In a baking dish, arrange the beets in a single layer and cover with the kosher salt. Roast for 1 hour, until tender; let cool slightly, then peel and quarter.
In a bowl, toss the beets with the orange juice, zest and 1 tablespoon of the olive oil. Season with sea salt and pepper.
Season the trout with salt and pepper. In a cast-iron skillet, working in 2 batches, heat 2 tablespoons of the canola oil until it shimmers. Cook half of the fillets skin side down over moderately high heat until golden, 3 minutes. Add half of the thyme and cook until the skin is crispy. Add half of the butter and turn the fillets; cook over moderate heat, basting, until just cooked through, 2 minutes longer; transfer to a plate. Discard the thyme.
Wipe out the skillet. Add the remaining 2 tablespoons of olive oil and the beet greens and cook, tossing, until just wilted, 2 minutes. Stir in the lemon juice and season with sea salt and pepper.
Serve the trout with the roasted beets and greens, spooning a tablespoon of crème fraîche on each plate.