Preheat oven to 350°F. Peel, core, and slice apples to about 3/8" to 1/2" inch in thickness. Transfer apples to a large mixing bowl.
Next, mix the granulated sugar, cinnamon, salt, cornstarch, lemon juice, and vanilla extract with the apples until they are well coated. Pour the apple mixture into a 9" skillet, forming an even layer. Finally, spread the 2 tablespoons of cold cubed butter evenly over the apples.
Sprinkle on an even layer of crisp topping. If you prefer crisper apples, bake for 35 minutes. For softer apples, bake for 40 minutes. Once the apple crisp is done, remove it from the oven and allow it to cool for about 10-15 minutes. You can serve it warm or at room temperature. Add a scoop of vanilla ice cream and a drizzle of caramel sauce to top it off. It's completely optional but delicious!