Prepare the pastry dough by combining flour, sugar, salt, and cinnamon in a food processor. Pulse in cold butter until mixture resembles coarse crumbs. Gradually add ice water until dough just comes together. Form into a disk, wrap in plastic, and refrigerate for 30 minutes.
Make the caramel sauce by combining sugar and water in a medium saucepan over medium heat. Do not stir! Let it cook until it turns amber (about 5-7 minutes). Remove from heat, carefully whisk in cream (it will bubble vigorously), then butter, vanilla, and salt until smooth. Set aside to cool slightly.
Prepare the apple filling by tossing diced apples with both sugars, flour, spices, salt, and lemon juice in a large bowl. Let sit for 10 minutes to allow flavors to meld and juices to release.
Preheat your oven to 375°F (190°C) and grease a standard 12-cup muffin tin generously with butter or cooking spray.
Roll out the chilled dough to about 1/8-inch thickness on a floured surface. Cut into 4-inch circles (a large cookie cutter or bowl works well). Gently press each circle into muffin cups, allowing the edges to extend slightly above the rim.
Spoon the apple mixture evenly into each pastry cup, filling them almost to the top. Drizzle each with about 1-2 teaspoons of the prepared caramel sauce, reserving some for serving.
Bake for 25-30 minutes until the crust is golden brown and the filling is bubbling. Look for caramelized edges—that’s where the magic happens!
Cool in the pan for 10 minutes, then carefully remove cups using a knife to gently loosen the edges. Transfer to a wire rack to cool for another 10-15 minutes.
Serve warm with an additional drizzle of caramel sauce and a small scoop of vanilla ice cream if desired.