Cut apples into bite-sized pieces.
A mix of green apples (like Granny Smith) and red apples (like Honeycrisp or Fuji) works best — the green apples bring tartness and structure, while the red apples add natural sweetness and become tender as they bake.
You can peel them, but keeping the skin adds texture, color, and extra fiber, so it’s both beautiful and nutritionally beneficial.

In a shallow baking dish, combine the apples with brown sugar, white sugar, cinnamon, lemon juice, and salt.
Toss gently to coat evenly, then set aside.
Tip: Lemon juice brightens the flavor and prevents browning, while salt enhances the natural sweetness of the apples.

In a bowl, combine oats, brown sugar, flour, cinnamon, and salt. Add softened butter and use your hands to mix until it forms coarse, sandy clusters with some larger crumbs.
If the mixture looks too dry, add a small amount of butter until it holds together in little clumps.
Tip: Cold butter gives a chunkier, crisper crumble; softened butter gives a softer, more cohesive topping. Either works — choose based on the texture you prefer.

Spread the crumble mixture evenly over the apples.
Bake at 350°F (175°C) for 40–45 minutes, until the apples are bubbling and the topping is golden.
If the crumble needs a bit more browning or crisping, continue baking in 3-minute increments until done.
Tip: For extra crunch, finish under the broiler for 1–2 minutes — but watch closely!

Scoop the warm crumble into bowls.
Top with vanilla ice cream, whipped cream, or enjoy it plain — the buttery apples and cinnamon crumble are satisfying on their own.