Preheat oven to 350°F (180°C). Spray a 10-inch cast-iron skillet with baking spray with flour.

In the bowl of a stand mixer fitted with the paddle attachment, beat butter, brown sugar, granulated sugar, and vanilla at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs, one at a time, beating well after each addition.

In a medium bowl, whisk together flour, cinnamon, baking powder, baking soda, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until almost fully combined. Fold in chopped apple and toffee. Spread dough in prepared skillet.

Bake until a wooden pick inserted in center comes out with a few moist crumbs, about 1 hour, loosely covering with foil during final 10 minutes of baking to prevent excess browning. Let cool for 5 minutes. Top with Caramel Apple Topping; serve warm with ice cream. Refrigerate in an airtight container for up to 2 days.