In a large pan of boiling water, cook the spaghetti, broccoli and peas together for 5 minutes.
Meanwhile, heat the oil in a pan and cook the onion until softened and turning golden. Add the garlic and cook for a further minute.
Drain the pasta and veg, reserving 4 tablespoons of the cooking water. Return the pasta and veg to the pan, stir through the smoked salmon, garlic and onion mixture, the crème fraîche, lemon juice, reserved pasta cooking water and the dill, until the pasta is well coated.
Season with freshly ground black pepper, sprinkle over the lemon zest to serve.
Cook's tip: you could substitute smoked salmon trimmings or cooked salmon for the smoked salmon.