Onion-marinated whole turkey with citrus compound butter and pan-dripping gravy

In a large food processor, process the onions, garlic, salt calculated from the bird's weight, black pepper, plenty of sumac and lemon juice to a fine paste; add stripped thyme leaves and process to a pulpy marinade.

Wearing gloves, separate the skin from the breast meat on both sides without tearing it, working deep into the breasts (from the other end if needed), then make pockets over the thighs around the drumsticks.

Pack the marinade into each pocket with a utensil and massage it to the ends; spread a couple of handfuls in the cavity and rub the rest over the skin.

Set in a roasting tray, wrap in plastic wrap and refrigerate two to three days.

Take the turkey out of the fridge for a couple of hours to come up to temperature.

Soften a stick of butter overnight, or in the microwave 30 seconds on low heat.

Zest four unwaxed lemons and two unwaxed oranges into the butter; add thyme, garlic cloves, a good amount of salt and equal amounts of black pepper, sumac and Aleppo pepper flakes, and mix to a compound butter.

On plastic wrap, pull all the marinade back out from under the skin by hand, scraping stuck onion off with a spatula; discard the marinade.

Line the tray base with thick slices of shallot and onion, orange and lemon, and some sage; set a wire rack over them to lift the bird out of the drippings for crisp skin, with a few slices on the rack so the skin does not stick.

Divide the butter into about four pieces, larger for the breasts and smaller for the thighs, push it under the skin and massage it to the edges; rub any extra in the cavity.

Stuff the cavity with the remaining aromatics, sage and a quartered onion, and tie the bird.

Insert one thermometer probe into the thickest part of the breast and one vertically into the thigh meat.

Coat the whole bird with a thin layer of olive oil; cover with non-stick foil (or baking paper under ordinary foil) and put in the oven.

Set the probe alarms: 69 degrees for the breast and 77 degrees for the thigh, as recommended by the app.

After about an hour and 10 to 20 minutes, remove the foil and cook uncovered until browned, re-covering the breasts if needed.

Remove the probes and rest the turkey before carving.

For the gravy, skim the fat from the drippings into a pan over high heat until sizzling; whisk in a few tablespoons of flour by eye and cook until the flour separates out of the fat again, cooking off the raw taste and browning it a little.

Add the drippings with their shallots, then chicken stock a bit at a time and about 500 ml more water to the texture wanted; blend smooth with a stick blender and check for salt.

Carve the rested turkey and serve with the gravy.