Mustard-Crusted Pork With Farro and Carrot Salad

Place pork on a wire rack set inside a large rimmed baking sheet; season all over with salt and pepper. Whisk mustard, mustard powder, and 1/4 cup oil in a small bowl to blend. Rub over pork and let sit at room temperature 1 hour. Preheat oven to 425 °F. Roast pork until beginning to brown, 25-30 minutes. Reduce heat to 350 °F and roast until a thermometer inserted in the thickest part registers 145 °F, 25-35 minutes longer, depending on thickness of roast. Meanwhile, cook farro in a large pot of boiling salted water until tender, 30-35 minutes; drain. Whisk vinegar, caraway seeds, honey, and remaining 1/4 cup oil in a medium bowl; set vinaigrette aside. Heat 2 tablespoons vinaigrette in a large skillet over medium-high heat. Add farro and carrots and cook, tossing often, until carrots soften and farro is warmed through, about 3 minutes. Remove from heat and transfer to a large bowl. Add onion, parsley, and half of remaining vinaigrette; season with salt and pepper and toss to combine. Slice pork. Serve with farro salad. Pass remaining vinaigrette alongside. DO AHEAD: Farro can be cooked 2 days ahead. Let cool, cover, and chill. Reheat before using.