Get that oven ready. Preheat your oven to 350°F and line an 8-inch square baking pan with parchment paper. Leave a little extra parchment hanging over the sides to create a sling. Trust me, future you will appreciate how easy it makes lifting these beauties out of the pan.

Make the shortbread crumble mixture. In a large-ish mixing bowl, combine your flour, sugar, baking powder, and salt. Give everything a quick stir to get the dry team acquainted.

Add your softened butter, egg, and vanilla extract. You can mix everything together with a fork if you're fancy, or you can do what I do and get in there with your fingertips. With clean hands, obviously. Because duh. Work everything together until you've got a soft, crumbly dough. It doesn't need to be perfectly smooth.

Make your crust. Set aside about one-third of your crumble mixture for the topping.

Press the remaining two-thirds into the bottom of your prepared baking pan, making it as even as possible. No need to get out a ruler. Just give yourself a nice, relatively level base for all those lovely apples.

Mix up the cinnamon apple filling. In a separate bowl, combine your finely diced apples, brown sugar, granulated sugar, cornstarch, cinnamon, nutmeg, lemon juice, vanilla extract, and a pinch of salt. Give everything a good stir until those apples are evenly coated in all that cinnamon-sugar goodness. Remember, smaller apple pieces are your friend here. They'll soften beautifully while baking and make slicing the finished bars much easier.

Put it all together. Spread your apple mixture evenly over the shortbread base. Then grab that reserved crumble mixture and scatter it over the apples. I like a mixture of big and little chunks, with some of the apple filling peeking through the spaces. It's supposed to look a little rustic. Perfectly imperfect. Just the way we like things around here.

Bake until golden and bubbly. Pop your pan into the preheated oven and bake for 40–45 minutes, or until the crumble topping is beautifully golden brown and the apple filling is bubbling around the edges. And just wait until you smell your kitchen. Oh. My. Goodness. If someone could figure out how to bottle the smell of cinnamon apples baking in the oven, I'd buy it by the gallon.

Let them cool. Remove your bars from the oven and let them cool completely in the pan, at least an hour, and longer if they're still warm. I know it's hard to wait, but this is what helps them hold together when you cut them. Once cooled, use your parchment sling to lift them out of the pan and cut into squares.