In a large bowl, toss the orange, blood orange, and clementine segments with granulated sugar and orange liqueur. Let sit at room temperature 20 minutes, stirring once, until the fruit releases its juice and turns glossy.

In a chilled mixing bowl, beat the heavy cream with an electric mixer on medium-high speed for about 2 minutes, until it holds soft peaks.

In a separate bowl, beat the mascarpone, powdered sugar, and vanilla until smooth and lump-free, about 1 minute.

Fold the whipped cream into the mascarpone mixture in two additions, keeping the mixture light and airy; stop folding as soon as no white streaks remain.

Scatter one third of the cake cubes over the bottom of a 3-quart trifle bowl, pressing lightly so they sit flat.

Spoon one third of the citrus segments and their juice over the cake, letting the liquid soak in.

Spread one third of the mascarpone cream over the fruit in an even layer, smoothing to the edges of the bowl so the next layer shows through the glass.

Repeat the cake, citrus, and cream layers two more times, finishing with a cream layer on top.

Cover and refrigerate for at least 2 hours, until the cake has softened and the layers hold their shape when sliced.

Just before serving, scatter pomegranate arils over the top and finish with torn pieces of gold leaf.