alex's slightly modified version of Food52's best apple crisp

click here for original recipe by Ella Quittner via Food52 

Crisp Topping:

- 2/3 cups almond meal (aka almond flour)
- 1 cup all-purpose flour
- 3/4 cup packed light brown sugar
- 1 teaspoon kosher salt
- 2 sticks butter, cold, cubed
- 1 1/3 cup rolled oats

Apple Mixture:

- 2 tablespoons freshly squeezed lemon juice
- 2 teaspoons cornstarch
- 2 tablespoons light brown sugar
- 2 teaspoons ground cinnamon
- 2 teaspoons apple pie spice/ pumpkin spice mix
- 1/4 teaspoon kosher salt
- 1 teaspoon freshly grated lemon zest
- 2 to 3 large apples—a juicy, firm variety, like Pink Lady, Honeycrisp, Jonagold, Braeburn, or a mix—peeled, cored, and cut into ~1/2-inch slices

- 2 large Granny Smith apples, peeled, cored and cut in to ~1/2-inch slices

1. Heat oven to 400°F.
2. In a large bowl, combine almond meal, flour, sugar, and salt, and whisk until integrated. Add the butter, and, using your hands, squish the butter into the dry ingredients to create small chunks. The mixture should look like wet sand and hold together when pinched, with some unblended butter streaks visible throughout. Add the oats and roughly mix in. Set in refrigerator to chill while you prepare the apples.
3. Whisk the lemon juice with the cornstarch, brown sugar, cinnamon, pie spice, salt, and lemon zest in a large bowl. Add the apple slices and toss gently until the slices are evenly coated. Transfer to a 8x8-inch baking dish (no need to grease it). You want about 1 inch of space between the apple slices and top of pan, so if you have too many apple slices, give them to the kids for a delicious snack.
4. Sprinkle the streusel evenly over the apples, breaking into olive-sized clumps where needed, and transfer to oven. Bake for about 30 minutes, rotating the pan halfway through, until topping is crisp all over and browning in spots, and the apple mixture is bubbling up at the sides. The apple pieces should be tender and easily pierced with a fork. (Note: If spots begin browning too deeply before the apples become tender, you can turn the temperature down to 375°F.) Let cool about 15 minutes before serving. I also enjoy this at room temperature with whipped cream.
5. Note: this recipe is very forgiving and can be easily 1.5x'd or doubled in a 9x13 pan.