Preheat the oven to 180˚C, gas mark 4. Butter then line a 900g loaf tin with baking parchment. Using electric beaters, beat the butter and sugar in a large bowl until creamy and very pale. Add about 1 tbsp egg, beat again until fluffy; repeat until all of the egg has been incorporated.
Sift in ½ the flour with the salt; fold in carefully with a spatula. Fold in the coconut cream until entirely combined, then the rest of the flour, to make a soft batter. Scrape into the tin, level the top and bake for 1 hour, until risen, golden and a skewer inserted into the middle comes out clean. Cool in the tin on a rack, until barely warm.
Sieve the passion fruit pulp over a bowl, pressing hard with a spatula to extract the juice. Rinse 2 tsp of the seeds; set aside. Mix the passion fruit juice (about 2 tbsp) with the lime juice. Poke holes all over the cake with a cocktail stick, then brush ½ the juice over the top. Add 75g sugar and the rinsed seeds to the remaining passion fruit juice (about 1 tbsp). Immediately spread over the cake. Allow to cool completely (overnight for maximum crunch) before serving.