Clean the whole Lochmuir salmon. Chop the pitted green olives.
- 1 Heat the oven to 190°/170°C fan/gas 5.
- 2 Halve the lemon, set one half aside and slice the other into rounds. To cook the salmon, start with two large sheets of foil, one on top of the other, in a roasting tin large enough to hold the whole fish. Brush the foil with 1 tablespoon oil and lay the salmon on top.
- 3 Stuff 4 tarragon sprigs, the lemon slices and a little salt and pepper in the cavity.
- 4 Dot the butter over the surface of the salmon and bring the foil around it in a loose parcel, sealing the edges tightly. Roast for 1 hour, then set aside to rest for 15 minutes before opening the foil.
- 5 Meanwhile, slice the squash into wedges, skin on, and toss with the remaining olive oil and the whole garlic cloves on a large baking tray.
- 6 Roast for 45 minutes, until the squash is golden then scatter with the pumpkin seeds and return to the oven for a final 5 minutes.
- 7 To make the mayonnaise, strip the leaves from the remaining tarragon sprigs and finely chop.
- 8 Stir into the mayonnaise with a squeeze of lemon juice from the remaining lemon half and the chopped olives.
- 9 Season with black pepper only. Serve the baked salmon with the roast squash, soft garlic and tarragon-olive mayonnaise.