This six-layer lemon cake is filled with passion fruit curd and creme fraiche mousse.
Heat oven to 350 degrees. Line 11 1/2-by-17 1/2-inch jelly-roll pan with parchment; brush with soft butter, and dust with flour, shaking out excess.
Place eggs and sugar in bowl of electric mixer. Using hand whisk, stir until mixed. Set bowl over pot of simmering water; whisk until mixture is warm, about 3 minutes.
Transfer bowl back to electric mixer; beat with whisk on high for about 7 minutes until, when whisk is lifted, mixture leaves trail resembling a ribbon that blends back into surface in 3 seconds. Add zest and juice. Sift flour over egg mixture, one-third at a time, folding after each addition. Just before final third is completely folded in, stream in butter; fold in. Pour into prepared pan; bake until cake tester comes out clean and cake is springy to the touch, 16 to 18 minutes. Cool. Invert pan to remove cake; peel off parchment.
Slice cake widthwise into three rectangles, about 5-by-11 inches each. Split each in half, creating two layers of equal thickness. Place one layer on a flat, rectangular platter; spread with 3/4 cup mousse. Spoon 1/2 cup curd over mousse; spread. Cover with another cake layer; repeat process ending with cake layer. Reserve 3/4 cup mousse to frost cake. Cover with plastic; chill about 4 hours or overnight.
When ready to serve, invert cake onto a serving plate. Spread top of cake with reserved mousse; sprinkle with coconut. Serve with passion-fruit pulp spooned around cake.