INGREDIENTS
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1 large sweet potato, peeled, halved, and sliced 1/2 inch thick
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3 large parsnips, peeled, halved, and cut into 2-inch pieces
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1 tablespoon finely grated peeled fresh ginger
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3 tablespoons olive oil, plus more for serving
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2 tablespoons light-brown sugar
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1/4 teaspoon cayenne pepper
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1 pork tenderloin (about 12 ounces), excess fat and silver skin removed
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Coarse salt
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1 bunch watercress, trimmed
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Lime wedges, for serving