1 1/2 pounds swordfish, cut into 2-by-1/2-inch strips
Salt and freshly ground pepper
1 medium onion, finely chopped
2 garlic cloves, minced
1/2 cup dry white wine
1 teaspoon finely grated lemon zest
1 1/2 tablespoons fresh lemon juice
1/4 cup chopped parsley
In a large pot of salted boiling water, cook the penne until al dente. Drain, reserving 1/2 cup of the pasta water.
Meanwhile, in a large, deep skillet, heat 2 tablespoons of the olive oil until shimmering. Season the swordfish with salt and pepper, add half to the skillet and cook over high heat until lightly browned and barely cooked through, about 2 minutes. Transfer to a large plate; repeat with 1 tablespoon of the olive oil and the remaining swordfish.
Add the remaining 1 tablespoon of olive oil to the skillet. Add the onion and garlic and cook over low heat until softened, about 5 minutes. Add the wine and simmer over moderately high heat until almost evaporated, about 3 minutes. Stir in the lemon zest and juice, penne and the reserved pasta water. Fold in the swordfish and the parsley, season with salt and pepper and serve.