Preheat your oven to 400°F (200°C). In a medium bowl, stir together the old-fashioned rolled oats, flour, dark brown sugar, chopped pecans, cinnamon, and salt.

Pour the warm browned butter over the dry oat mixture and toss with a fork until large, buttery streusel clumps form. Set aside.

Melt 2 tablespoons butter in a 10-inch cast-iron skillet over medium-high heat. Add the sliced apples, dark brown sugar, cinnamon, apple cider, cornstarch, and vanilla. Sauté for 5 minutes until the apples are slightly tender and coated in a glossy bubbling caramel.

Remove the skillet from the burner and scatter the clumpy brown butter oat streusel evenly over the hot apples.

Transfer the skillet to the 400°F oven and bake for 15 minutes until the oat topping is deeply golden-crisp and the apple caramel is bubbling up around the edges. Cool for 5 minutes, then top with vanilla ice cream and salted caramel drizzle.