Place the apples in a large bowl and mix together with ½ cup sugar. Transfer to a colander over a large bowl (or in the sink) and let rest for 30 minutes.
2 lbs Granny smith apples, 1 lb Gala apples, 2¾ cups sugar
Meanwhile, in a medium-sized bowl, mix together ¼ cup sugar, flour, cinnamon, and nutmeg. Set aside.
⅓ cup all-purpose flour, ½ tsp ground cinnamon, ¼ tsp ground nutmeg
Preheat oven to 350°F.
In a medium-sized saucepan, bring 2 cups of sugar and ½ cup of water to a boil over high heat, stirring occasionally. Reduce the heat to medium-high, and stop stirring the mixture. Every couple of minutes, gently lift the pan and swirl the mixture. It should be bubbling fairly strongly. Continue this process until it has turned amber in color, usually about 15 minutes. Turn off the heat and carefully stir in the butter, heavy cream, and salt. Stir and then let rest for 15 minutes.
½ cup water, ¼ cup unsalted butter, ½ cup heavy cream, ½ tsp Kosher salt
Place the prepared apples in a large bowl and stir in the sugar/cinnamon mixture. Stir until fully coated.
On a lightly floured surface, roll out the pie dough into a 12-inch circle. Transfer the dough to a pie dish and press the bottom and sides into the dish. If desired, trim and then crimp the edges (see video for visual guidance).
1 pie dough
Transfer all of the apples to the pie dish with the dough. There should be enough apples to form a dome. Pour about ⅔ of the caramel over the top of the apples, saving the rest for future drizzling.
In a small bowl, combine the oats, flour, brown sugar, cinnamon, and salt. Use a fork (or two) to work the butter into the mixture. Sprinkle the topping all over the top of the pie.
4 tbsp old-fashioned oats, 2 tbsp all-purpose flour, 3 tbsp brown sugar, ¼ tsp ground cinnamon, ¼ tsp Kosher salt, 3 tbsp unsalted butter
Bake the pie for 90 minutes. You may need to cover the edges with foil or a pie crust protector if getting too dark (usually after about 1 hour).
Remove from oven and let cool completely before serving.
To serve, slice cooled pie and, if desired, heat the remaining caramel in your microwave on HIGH until pourable. Drizzle warm caramel over the top of the pie slices.