Preheat and prep: Heat the oven to 350°F (175°C). Grease a small baking dish or 8-inch skillet with butter or coconut oil.

Slice the apples: Peel, core, and thinly slice the apples. If using zucchini or chayote for a mix, peel and slice them to match the apple thickness for even cooking.

Season the filling: In a bowl, toss the slices with 1–2 tablespoons granular sweetener, 1 teaspoon cinnamon, a pinch of nutmeg, 1–2 teaspoons lemon juice, and 1/2 teaspoon vanilla. If you want a thicker sauce, sprinkle in 1/8 teaspoon xanthan gum and toss well.

Make the crumble: In a separate bowl, combine 1 cup almond flour, 1/3 cup chopped pecans or walnuts, 1/4 cup granular sweetener, 1 teaspoon cinnamon, a pinch of salt, and 1 tablespoon coconut flour (optional for extra crispness). Stir in 4 tablespoons melted butter until clumps form.

Assemble: Spread the fruit mixture in the prepared dish. Sprinkle the crumble evenly on top, pressing gently to help it hold together.

Bake: Bake 22–28 minutes, until the topping is golden and the fruit is tender. If the top browns too fast, tent loosely with foil for the last few minutes.

Rest: Let it cool 10 minutes. This helps the juices settle and the topping crisp up further.

Serve: Spoon into bowls. Add a small dollop of whipped cream or a scoop of keto ice cream if you like.