Heat a large non-stick frying pan over medium heat. Add the oil and salmon, skin-side down, and cook for 4–5 minutes each side. Set aside and keep warm.
Heat the butter in a large non-stick frying pan over medium heat. Add the onion and garlic and cook for 3–4 minutes or until tender. Add the zucchinis, spinach, capers, lemon rind, parsley, cream, salt and pepper and cook for 1–2 minutes or until the spinach is wilted. Serve the salmon on the wilted greens. Serves 4.