Preheat your oven to 350°F (175°C).

Cream the softened unsalted butter and light brown sugar until creamy and light in color, about 2-3 minutes.

Add ground cinnamon, salt, baking soda, and all-purpose flour; mix on low speed until crumbly, about 1-2 minutes.

Set aside 1 cup of the crumb mixture. Press the remaining mixture into the bottom of a lined baking sheet. Bake for 12 minutes.

While the crust is baking, prepare the apples by quartering, coring, and thinly slicing them.

Melt together unsalted butter, light brown sugar, and granulated sugar in a saucepan. Stir in cream and simmer until thickened, about 5-7 minutes.

Drizzle the caramel over the sliced apples and sprinkle the reserved crumb mixture on top. Optionally, add turbinado sugar.

Bake for an additional 30-35 minutes, until golden brown and the apples are tender.

Let cool on a wire rack for at least 15-20 minutes before slicing.

Slice into squares and serve, optionally with vanilla ice cream.