Heat oven to 450°F Spray bottoms and sides of 6 (6-oz) custard cups with baking spray with flour. Sprinkle 1 teaspoon cracker crumbs onto bottom and around side of each cup.
In large bowl, beat whole eggs and egg yolks with wire whisk until well blended. Beat in brown sugar. Beat in caramel topping and flour until well blended. Stir in apple. Divide batter evenly among custard cups. Place cups on cookie sheet with sides.
Bake about 15 minutes or until sides are set and centers are still soft but not liquid (tops will be slightly puffed). Watch carefully—cakes can overbake quickly. Remove from cookie sheet. Let stand 3 minutes.
Run small knife or metal spatula along sides of cakes to loosen. Immediately place heatproof dessert plate upside down over top of each cup; turn plate and cup over. Remove cup. Sprinkle cakes with powdered sugar. Serve warm.