Step 1: Preheat oven to 325°F and line 9x13 inch baking pan with parchment paper.
Step 2: Mix graham cracker crumbs, sugar, melted butter, and salt. Press into pan bottom. Bake 8-10 minutes until golden. Cool 5 minutes.
Step 3: Beat softened cream cheese until fluffy. Add sugar, sour cream, and vanilla. Mix in eggs one at a time on low speed. Fold in flour gently.
Step 4: Pour cheesecake filling over cooled crust. Bake 20-25 minutes until edges set but center jiggles slightly.
Step 5: Heat butter in skillet. Add sliced apples, brown sugar, cinnamon, nutmeg, ginger, and lemon juice. Cook 5-7 minutes until tender. Add cornstarch and stir 1 minute.
Step 6: Spread apple mixture evenly over baked cheesecake layer.
Step 7: For caramel: Heat sugar in heavy saucepan over medium-high heat until amber colored (5-7 minutes). Remove from heat. Add butter carefully. Let bubble settle, then stir in heavy cream, vanilla, and salt.
Step 8: Drizzle caramel over apple layer. Bake additional 10-12 minutes.
Step 9: Cool completely at room temperature for 2 hours, then refrigerate at least 4 hours (overnight is best).
Step 10: Cut into 12 squares using a knife dipped in hot water. Serve cold or at room temperature.