Melt butter in a heavy bottom sauce pot over medium-low heat and add apples. Mix to coat apples with butter.
Sprinkle apple pie spice, sugar, and flour over the apples and mix well, until ingredients are evenly incorporated. Add lemon juice and mix.
Cover and cook for about 10 minutes, until apples give out its natural juices and start to soften. Take off heat.
Oat Topping:
In a large mixing bowl, combine all dry ingredients for the oat topping and mix well, until evenly incorporated.
Pour in melted butter all over and mix very well. Feel free to use your hand to make sure butter and ingredients are mixed very well.
Apple Crisp:
Preheat the oven to 350° and rub inside of a 9x9 baking dish with butter, all over the bottom and up the sides.
Spread apple topping evenly in the dish.
Spread oat topping evenly over the apples.
Bake for 35-40 minutes, until topping is golden brown and apples bubble.
Notes
Gluten Free Notes: To make this apple crisp gluten free, make sure to substitute the flour in the apple filling and in the crisp topping with a gluten free all purpose flour. All of the remaining ingredients should already be gluten free, but double check the packaging just in case.
Additional Flavors: Try adding other fruit like pears, Asian pears, peaches, plums, cherries, or nectarines. Add berries like blueberries or raspberries. Feel free to add some nuts like pecans, walnuts, and almonds – they all make a great compliment to apple crisp.
Apple pie spice: this is a spice mix you can find in post grocery stores. Apple pie spice is a blend of ground cinnamon, nutmeg, and allspice. To make your own, simply combine 2 tablespoons of ground cinnamon with 2 teaspoons or ground nutmeg and 1 teaspoon of ground allspice. Mix it all together and store in a small glass jar with a lid.