Put 1 tbsp oil in a pan, add the onion and red pepper and cook until soft. Blend the anchovies, capers, garlic, half the parsley, half the dill and the lemon juice into a paste using a hand blender. Add the remaining oil, herbs and lemon zest to this pesto.
Cook the linguine according to the pack instructions and drain thoroughly. Add the pasta to the onion mix, then the prawns and the anchovy pesto, and stir in well. Season with the pepper.
Serve with mixed salad leaves.