Drain the pineapple well. Separate 2 eggs. For the macaroon mixture, beat the egg whites with 1 pinch of salt and lemon juice until very stiff, while pouring in 80 g of sugar. Mix grated coconut and ¼ tsp. baking powder and fold into the beaten egg white.
Cold. Grease a springform pan (26 cm Ø). Preheat oven (electric cooker: 180 °C/circulating air: 160 °C/gas: see manufacturer).
For the dough, mix 150 g butter, 150 g sugar and 1 pinch of salt with the whisk of the mixer until white-creamy. Stir in the egg yolks and 2 eggs separately. Mix flour, 1⁄2 packet baking powder and cocoa, stir in milk and rum.
Place the pineapple on the bottom of the mould. Spread the macaroon mixture on top and then the sponge mixture. Bake in the oven for about 50 minutes.
Let the cake cool down a little in the mould, loosen it at the edge of the mould and then turn it over onto a cake plate. Let it cool down.