1.Preheat oven to moderate, 180°C (160°C fan-forced). Line two large oven trays with baking paper.
2.In a food processor, process macadamias until finely ground. Combine macadamias, brown sugar and cardamom in a small bowl.
3.Lay a sheet of pastry on a clean board. Brush with a little melted butter; sprinkle with a thin layer of nut mixture. Repeat with remaining pastry, butter and nut mixture. Press down lightly.
4.Cut 6 x 12cm rounds from layered pastry; discard excess. Carefully transfer layered rounds to one oven tray. Cover pastry with a sheet of baking paper, then top with the second tray.
5.Peel and quarter pineapple. Remove core; thinly slice. Place pineapple in a single layer on top tray.
6.Bake trays together 20 minutes. Remove top tray and baking paper on top of pastry. Place pineapple on pastry rounds. Sprinkle with caster sugar. Bake a further 10 minutes, or until pastry is crisp and golden.
7.Serve tarts with vanilla ice-cream.