Heat the oven to 350 degrees. Lightly grease a 9-by-12-inch baking dish with oil spray or butter.
I leave the peel on the apple, but you can peel them if you prefer. Chop the apples into 1/4-inch dice and place them in the baking dish.
Add the maple syrup, apple cider, cinnamon, salt, and cornstarch on top of the apples. Toss, using a spoon or your hands, to coat the apples and make sure everything is well mixed. Spread the apples into an even, flat layer.
Melt the butter and add to a large bowl. Mix in the maple syrup.
Add the flour, oats, cinnamon, pumpkin spice, salt, and baking powder to the bowl. Mix until everything is combined and forms a crumbly but moist mixture.
Crumble the topping over the apples, covering them completely. I like to squeeze the mixture in my hand then sprinkle it over to create some large clumps of the topping.
Bake the apple crisp until the topping is golden brown, about 40 minutes. Cover the crisp with aluminum foil and bake for an additional 20 minutes. This will ensure the apples get completely soft and the topping doesn't get too brown.
Allow the crisp to cool for 15 to 20 minutes then serve. The crisp can be made a day ahead and stored at room temperature. You can reheat it in a 350 oven for 10 to 15 minutes before serving if you'd like.