Prepare Cake: Preheat oven to 350°F (175°C). Grease, line, and flour two 8-inch and two 6-inch pans.

In a large bowl, whisk cake flour, sugar, baking powder, baking soda, and salt. In a separate bowl, cream softened butter and coconut oil until fluffy. Beat in eggs, followed by coconut milk and extract.

Gradually add dry ingredients to wet, mixing just until combined. Fold in toasted shredded coconut and well-drained crushed pineapple. Divide batter between prepared pans and bake for 30-35 minutes.

Make Curd: In a non-reactive saucepan, simmer passionfruit juice and 1/2 cup sugar until dissolved. In a small bowl, whisk egg yolks, lemon juice, and salt. Temper the yolk mixture with a small amount of the hot juice, then return the entire mixture to the saucepan.

Cook curd over low heat, whisking constantly, until thickened and coats the back of a spoon. Strain through a fine sieve and whisk in the cubed unsalted butter. Cool to room temperature, cover with plastic wrap touching the surface, and chill until firm (at least 4 hours).

Make Buttercream: Beat egg whites and cream of tartar to soft peaks. In a small saucepan, boil granulated sugar and water to the soft-ball stage (240°F/115°C). With mixer running on low, carefully pour the hot sugar syrup into the egg whites in a slow, steady stream. Increase mixer to high and beat until stiff, glossy meringue is formed and the bowl is cool. Gradually add softened butter, cube by cube, until a smooth buttercream forms.

Level chilled cakes. Divide buttercream into bowls. Keep one white. Tint the others to precise sunset shades (hot pink, vibrant coral, lighter peach, cream).

Assemble: Stack the two 8-inch cake layers on a plate, crumb coating the center with white buttercream. Place another cake on top. Insert structural dowels into the bottom tier, cutting them flush. Place a 6-inch cake board on top. Stack and crumb coat the two 6-inch layers. Crumb coat the entire surface of both tiers and chill for 30 minutes to set.

Frost Ruffles: Fit a piping bag with a large petal tip. Starting at the base of the bottom tier, apply a thick row of continuous ruffles using the deep hot pink buttercream. Change color every few rows to create your sunset gradient, finishing with cream on the top tier. Chill for 1 hour to set.

Decorate: Tint fondant to create palm trees (brown trunks, orange fronds) and a woven yellow hammock. Sculpt plumeria or hibiscus-style flowers. Allow decorations to set, then place them on the chilled cake using a gentle press to secure.

Finish with Gloss and Butter: Brush a generous layer of clear vanilla glaze over the entire surface, decorations, top, and ruffles. Let pool and create mirror pools at the base border. Drizzle melted brown butter mixed with extra passionfruit curd over the glaze to create complex dripping effects.

Rest and Serve: Allow the cake to rest at cool room temperature for 10 minutes before slicing. Use a hot serrated knife to cut clean slices showcasing the dense cake layers, passionfruit curd filling, and complex ruffled buttercream. Serve immediately with a shiny spoon.