Method

• 1.
  Preheat the oven to 180°C. Grease and line the sides of a 23cm round springform cake pan.

• 2.
  Place 80g butter and the brown sugar in a small saucepan over medium heat. Stir to dissolve the sugar. Continue to cook, without stirring, for 3-4 minutes until a dark caramel. Stir in the lime zest, then remove from heat and pour into the prepared cake pan. Arrange the pineapple slices and crystallised ginger in an even layer on top of the caramel. Set aside while you make the cake batter.
• 3.
  Meanwhile, in a bowl, sift together the flour, baking powder, ground ginger and 1/4 teaspoon salt. Using an electric mixer, beat caster sugar and remaining 120g butter until light and fluffy. Scrape down the sides of the bowl and beat in vanilla seeds. Add the egg yolks, one at a time, beating well after each addition.
• 4.
  In three batches, alternately beat the flour mixture and milk into the egg yolk mixture, until a smooth batter forms.
• 5.
  In a separate clean, dry bowl, whisk the eggwhites with the cream of tartar until soft peaks form. Mix 2 tablespoons eggwhites into the cake batter. In batches, gently fold in the rest of the eggwhites, using a large metal spoon, being careful to keep in as much air as possible. Pour the batter into the cake pan and bake for 1 hour or until a skewer inserted in the centre comes out clean. (Cover the surface with foil if browning too quickly.)
• 6.
  Remove cake from the oven and place on a wire rack to cool for about 15 minutes. Run a sharp knife around the edge of the pan, then invert the cake onto your serving plate. Serve warm or at room temperature with softly whipped thickened cream.