Preheat the oven to 375 degrees. Heat the oil in a large cast iron pan or oven-safe skillet over medium heat. Once oil is shimmering, add the onions and cook, stirring often, for 7 to 10 minutes or until softened and slightly brown. Add garlic and cook for 30 seconds or until fragrant. Add the tomatoes, paprika, tomato paste, wine (or broth), half of the parsley and raise heat to medium-high and bring to a simmer. Let simmer uncovered until the sauce cooks down by one-quarter, about 15 minutes. Add the zucchini noodles and toss well to combine. Make 4 cavities in the veggies and add the fish fillets. Cover with an oven-safe lid, if available.

Place the fish in the oven and bake until fish is opaque and flakes with a fork, about 30 minutes. Garnish immediately with remaining parsley. Serve.