Preheat the oven to 375 degrees F. Season the fish with salt and pepper. Heat 1 tablespoon butter in a large nonstick skillet over medium-high heat. Sear the fish until golden brown on one side, about 3 minutes. Transfer to a rimmed baking sheet, cooked-side up, and roast in the oven until just cooked through, about 10 minutes.
Meanwhile, melt the remaining 3 tablespoons butter in the skillet over medium-high heat. Add the cauliflower and cook, stirring, until golden brown and crisp-tender, about 6 minutes. Add the almonds, raisins, coriander, 1/4 teaspoon salt, and pepper to taste; cook until the almonds are golden, about 2 minutes. Remove from the heat and stir in the lemon juice and parsley.
Divide the fish among plates and serve with the cauliflower and lemon wedges.