Sweet and sour with a nice crunch—there's nothing not to like about this colorful dessert!
Using a sharp knife, cut peel and white pith from oranges. Slice into rounds; arrange on platter. Drizzle with liqueur. In saucepan, stir sugar and 2 tbsp. water over medium-high until sugar dissolves. Boil without stirring, swirling pan often and brushing sides with wet pastry brush, until the caramel is deep amber, about 8 minutes. Immediately pour over oranges. Let stand 15 minutes. Top with mascarpone and some zest.