Toss the tomatoes with the garlic, onion, oil, salt and pepper.
Insert a piece of garlic into the flesh of each tomato half. Transfer the tomatoes, cut side down, to a roasting pan. Scatter onions over top. Roast in 425ºF (220ºC) oven for 40 minutes or until softened.
Remove the shrivelled skins from the tomatoes using a pair of tongs.
Toss the mushrooms with pesto and vinegar; add to the roasting pan. Roast for 10 minutes or until heated through.
Break up the tomatoes and garlic into a slightly chunky sauce using the edge of a spoon. Add the pasta, turkey and parsley to the pan; toss with the vegetable mixture, scraping up any browned bits.