Heat oven to 180°C (160°C for dark or nonstick pan).
Make cake as directed on box for 33 x 23cm pan; cool 15 minutes. Poke holes halfway into cake every 5cm, using handle of wooden spoon; evenly pour 250 grams caramel topping over holes. Cool completely, about 1 hour. Spread frosting evenly over cake.
Dip cut edges of apple wedges into orange juice to prevent browning; slightly pat dry. Dip uncut edges into 85 grams caramel topping; roll in nuts. Cover and refrigerate. Just before serving, place an apple wedge on each serving of cake. Store cake loosely covered; cover and refrigerate any remaining apple wedges.