Instructions

Whisk ½ cup sugar, 3 large eggs and 5 large yolks, and pinch salt in medium bowl until smooth. Warm 1 cup pineapple juice and ¼ cup lime juice in small saucepan over medium heat until just bubbling around edges, 1 to 2 minutes. Whisking constantly, slowly pour hot juice mixture into sugar mixture in bowl, whisking until smooth and fully combined. Transfer mixture to now-empty saucepan and cook over medium heat, stirring constantly, until mixture registers 170 degrees and is thick enough to cling to spoon, about 3 minutes.
Immediately pass curd through fine-mesh strainer into clean bowl. Press lightly greased parchment paper directly on surface of curd and refrigerate until cool, at least 30 minutes or up to 24 hours.
Meanwhile, whisk remaining 1 cup pineapple juice, ½ cup coconut cream, ½ cup rum, remaining 2 tablespoons lime juice, 1 tablespoon sugar, and pinch salt together in shallow dish to dissolve sugar; set soaking mixture aside.
Using stand mixer fitted with whisk attachment, whip 12 ounces mascarpone and remaining ¾ cup coconut cream on medium speed until no lumps remain, about 1 minute, scraping down bowl once or twice. Add 3 tablespoons sugar and remaining ¼ teaspoon salt and continue to whip until just combined, about 1 minute longer. Transfer to large bowl.
In now-empty mixer bowl, whip cream on medium speed until frothy, about 1 minute. Add remaining 1 tablespoon sugar; increase speed to high; and continue to whip until cream holds stiff peaks, 1 to 1½ minutes longer. Fold one-third of whipped cream into mascarpone mixture to lighten, then gently fold in remaining whipped cream until well combined. (Whipped mascarpone mixture can be refrigerated for up to 24 hours.)
Whisk soaking mixture to recombine. Working with 1 ladyfinger at a time, roll in soaking mixture (do not submerge; rolling should take about 2 seconds for each cookie), remove, and shake off excess liquid. Place soaked cookie in dish. Continue rolling and shaking with half of ladyfingers, arranging them in single layer in 13 by 9-inch glass or ceramic baking dish, breaking or trimming as needed to fit neatly into dish. Spread half of mascarpone mixture evenly over ladyfingers in dish.
Spread cooled pineapple-lime curd over top, using offset spatula to smooth and spread mixture to sides and into corners of dish. Repeat dipping and arranging remaining ladyfingers, then spread remaining mascarpone mixture over ladyfingers. Wipe edges of dish with dry paper towel. Cover and refrigerate for 6 to 24 hours. Sprinkle with 2 teaspoons lime zest and ¾ cup toasted coconut flakes just before serving