Making the Filling

Preheat the oven to 375ºF. Slice the apples into 1/4 inch slices.

In a large bowl, toss the apple slices in the lemon juice and vanilla.

In another bowl, mix together the light brown sugar, cornstarch, and apple pie spice.

Toss the lemon coated apples in the sugar mixture until evenly coated.

Pour the seasoned apples into the skillet.

Making the Crumble

Finely crush the cinnamon graham crackers, avoiding any large pieces.

In a medium bowl, mix the crushed graham crackers, light brown sugar, and kosher salt together.

Add the melted butter and vanilla to the graham cracker mixture. Stir until completely combined.

Assembly

Pour the cinnamon graham cracker crumble on top of the apple slices in the skillet.

Firmly press the crumble into the apples to ensure an even layer on top and prevent any of the crumble from spilling out of the skillet.

Place the skillet in the oven and bake for 45-50 minutes until the crumble is crispy golden brown. Top with freshly grated lemon zest while warm and serve with vanilla ice cream.