Preheat oven to 220C/200C fan-forced. Grease and line a large baking tray.
Place potato in large saucepan of cold water and cover with a lid. Place over high heat and bring to a boil. Boil, uncovered, for 6-8 minutes or until potato is almost tender. Drain.
Return potato to saucepan and place over low heat. Shake pan for 1 minute or until excess water evaporates and to rough edges of potato.
Combine ⅓ cup mayonnaise and garlic powder in a large bowl and season. Add potato and toss to coat.
Drizzle 1 tbsp of the remaining mayonnaise on prepared tray. Top with potato mixture and spread out to a single layer. Drizzle with remaining mayonnaise and bake for 30 minutes. Turn potato and bake for a further 15 minutes or until potato is golden and tender. Serve with extra mayonnaise.
