1Heat oven to 350°F (325°F for dark or nonstick pan).
2Make cake as directed on box for 13x9-inch pan; cool 15 minutes. Poke holes halfway into cake every 2 inches, using handle of wooden spoon; evenly pour 3/4 cup caramel topping over holes. Cool completely, about 1 hour. Spread frosting evenly over cake.
3Dip cut edges of apple wedges into orange juice to prevent browning; slightly pat dry. Dip uncut edges into 1/4 cup 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.