Preheat your oven to 350 degrees F. Grease a 9x13-inch baking dish very generously with softened butter or cooking spray, making sure you coat the corners and all the way up the sides. Do not skimp here. The sauce bubbles up high during baking and will cement itself to any bare spots.

Toss the sliced apples with 1 teaspoon of the cinnamon and 2 tablespoons of the brown sugar in a bowl and set aside.

Make the sauce: melt the butter in a small saucepan over medium heat. Stir in the remaining brown sugar, heavy cream, salt, and the remaining 1 teaspoon of cinnamon. Cook, stirring constantly, for 2 to 3 minutes until the sugar dissolves and the sauce is smooth and slightly thickened. Remove from heat and stir in the vanilla.

Open the biscuit cans and separate each biscuit. Cut each biscuit into quarters. Scatter half the biscuit pieces in a single loose layer in the greased baking dish. Tuck the cinnamon apple slices evenly over the biscuit layer, then scatter the pecans over the apples. Add the remaining biscuit pieces on top. They do not need to be perfectly arranged. Gaps and layers are fine and make it pull-apart.

Pour the warm brown sugar butter sauce slowly and evenly over the entire top of the assembled casserole. Use a spatula to coax the sauce into any visible gaps around the edges.

Bake uncovered on the center rack for 30 to 35 minutes. The top should be deep golden brown and the sauce should be visibly bubbling around the edges. If the top is browning too fast after 25 minutes, lay a loose sheet of foil over it for the remaining time.

Let the casserole rest in the pan for 5 minutes before serving. Use a large spoon to scoop portions into bowls, making sure each serving gets plenty of the caramel sauce from the bottom of the pan. Serve warm.