Preheat oven to 225°F. Cut lemon into thin slices and place on a baking sheet.
Rub halibut with olive oil, salt and spices. Place on lemon slices on sheet tray, place the halibut fillet on top, and roast 40-50 minutes until the flesh flakes easily in the middle, and temperature reaches 125F.
To serve, break fish into big chunks and top with herb salsa.
Finely dice shallot. Place in a small bowl, cover with vinegar, and allow to sit for 15 minutes.
Finely mince 1/4 cup parsley leaves. Combine in a separate small bowl with olive oil and a hefty pinch of salt.
Just before serving, use a slotted spoon to add the shallot (but not vinegar) to the parsley oil. Stir and taste for salt, adding more vinegar if desired. Serve on top of and alongside cooked fish.