Preheat oven to 180°C (160°C fan-forced). Grease the base and sides of a 24 cm round cake tin with the softened butter (I like to use a pastry brush).
Dissolve sugar in water over medium heat and cook for few minutes until golden brown.
Pour the caramel over the base and sides of the tin, ensuring to coat it as evenly as possible.
Halve the pineapples and cut out the cores. Cut the fruit into thick slices and arrange the over the base of the tin. Poke any smaller pieces in the gaps.
Combine the flour, baking powder, salt, sugar and 1 tbsp of the ground almonds in a bowl. Reserve the remaining ground almonds to sprinkle on top of the cake.
To make the cake batter, cream the butter and sugar in an electric mixer until light and fluffy.
Gradually add the dry ingredients and the beaten eggs, alternating between each addition.
Spoon the cake batter over the pineapple base, smooth the top with a spatula and sprinkle the remaining ground almonds on top.
Bake the cake for about 50 minutes until golden on top, and an inserted skewer comes out clean.
Let the cake cool for a few minutes in the tin, run a knife around the edge of the tin, then invert the cake onto a plate. Let it sit for a minute before gently easing the tin off the top. Spoon any leftover remaining pineapple and sauce from the tin over the cake.
Serve the cake warm with a dollop of thick cream or yoghurt.