Whisk flour, brown sugar and apple pie spice in bowl to blend.
Add butter and rub in with finger tips or pastry blender until the size of peas. Mix in almonds; set aside.
Preheat oven to 350ºF. Butter 13x9 inch baking dish.
In large bowl, whisk sugar, flour, zest and apple pie spice. Add apple slices and vanilla; toss to coat. Spoon filling into prepared dish. Sprinkle topping over.