Chop the rhubarb into 1-inch pieces and combine with 200 grams of sugar and juice of two oranges in a pot. Cook covered over medium-low heat for 5 minutes.

Remove the lid and stir occasionally for 10-15 minutes until thickened and syrupy. Set aside to cool.

In a saucepan, whisk together corn starch and 100 grams of sugar. Gradually add the milk, egg yolks, salt, vanilla, and cardamom. Cook over medium-low heat for about 10 minutes until thickened.

Remove from heat and whisk in butter. Allow custard to cool.

Whip the heavy cream with additional sugar until medium peaks form. Gently fold into the cooled custard.

In a trifle dish, layer Nilla wafers, custard, rhubarb compote, and raspberries. Repeat the layers, finishing with custard or whipped cream.

Cover with plastic wrap and refrigerate for at least 12 hours before serving. Garnish with fresh raspberries if desired.