Question: Inverallochy Castle lies .5 miles south of what z-plan castle that was described as one of the nine castles of the Knuckle?

Context paragraphs:
Inverallochy Castle: Inverallochy Castle is a ruined courtyard castle near the village of Inverallochy in the Buchan area of north-east Scotland.  It lies 0.5 mi south of Cairnbulg Castle near Fraserburgh.  It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Castle Fraser: Castle Fraser is the most elaborate Z-plan castle in Scotland and one of the grandest 'Castles of Mar'.  It is located near Kemnay in the Aberdeenshire region of Scotland.  The castle stands in over 300 acre of landscaped grounds, woodland and farmland which includes a walled kitchen garden of the 19th century.  There is archaeological evidence of an older square tower dating from around 1400 or 1500 within the current construction.

Nine castles of the Knuckle: The nine castles of the Knuckle are a group of ancient castles found in Aberdeenshire in the Buchan area of Scotland.  The term was used by historian William Douglas Simpson, who described the promontory between the Moray Firth and the North Sea as "the north-eastern knuckle of Scotland".  From west to east, the castles are Dundarg, Pitsligo, Pitullie, Kinnaird, Wine Tower, Cairnbulg, Inverallochy, Lonmay and Rattray.  Although Simpson coined the term, he did not draw any connections between the sites, other than their location.

Dundarg Castle: Dundarg Castle is a ruined castle about 2 km north-northeast of New Aberdour, Aberdeenshire, Scotland, built within the ramparts of an earlier iron age promontory fort.  It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Castle of Rattray: The Castle of Rattray was a medieval Scottish castle, with multiple variations on its structure over approximately six centuries.  Originally built as a ""late 12th- or early 13th century defensive motte"" it provided protection for Starny Keppie harbour and Rattray village.  Sometime between 1214 and 1233 it was upgraded by William Comyn, jure uxoris Earl of Buchan before being destroyed in the 1308 Harrying of Buchan.  After Comyn's timber castle was burned down it was replaced by a stronger stone castle which was engulfed during a 1720 sand storm along with nearby Rattray village.  After the storm, the castle was not dug out and remains covered to this day.  The castle was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Kinnaird Head: Kinnaird Head (Scottish Gaelic: "An Ceann Àrd" , "high headland") is a headland projecting into the North Sea, within the town of Fraserburgh, Aberdeenshire on the east coast of Scotland.  The 16th-century Kinnaird Castle was converted in 1787 for use as the Kinnaird Head Lighthouse, the first lighthouse in Scotland to be lit by the Commissioners of Northern Lights.  Kinnaird Castle and the nearby Winetower were described by W. Douglas Simpson as two of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.  Both buildings are category A listed buildings.

Pitsligo Castle: Pitsligo Castle is a ruined castle half a mile east of Rosehearty, Aberdeenshire, Scotland.  It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Cairnbulg Castle: Cairnbulg Castle is a z-plan castle situated in Cairnbulg, Aberdeenshire, Scotland.  It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Beldorney Castle: Beldorney Castle is a Z-plan castle dating from the mid-16th century, about two miles south of Glass, in hilly country in the valley of the Deveron, in Aberdeenshire, Scotland.

Pittulie Castle: Pittulie Castle, also spelled as Pitullie Castle, is an oblong tower house probably dating from the late 16th century, half a mile from Pitsligo Castle, Rosehearty, Aberdeenshire, Scotland.  It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.

Supporting paragraphs: Inverallochy Castle Cairnbulg Castle
Answer: Cairnbulg Castle