Scatter sugar in the base of a large frying pan and cook over medium-high heat, shaking pan occasionally, until sugar is dark and caramelised (4-5 minutes). Add 100ml water (be careful, hot caramel will spit), swirl pan to combine, then add peppercorns and vanilla bean (reserve seeds).
Meanwhile, quarter pineapple lengthways through the core, remove core and discard. Add pineapple to caramel and cook, turning occasionally, until glazed and tender (4-5 minutes).
Stir yoghurt and vanilla seeds in a bowl to combine and serve with pineapple and spiced caramel.