Preheat convection oven to 190°C (375°F).

In a large mixing bowl, combine sliced apples, strawberries, granulated sugar, lemon juice, and 2.5g of ground cinnamon.

Transfer the fruit mixture into a 23cm square ceramic baking dish, ensuring even distribution.

In a separate bowl, whisk together flour, oats, brown sugar, salt, and the remaining 2.5g of ground cinnamon.

Incorporate the chilled, cubed butter into the dry mixture using a pastry blender or fingertips until pea-sized crumbs form.

Distribute the crumble topping uniformly over the fruit base.

Bake for 40 to 45 minutes until the fruit juices exhibit high viscosity and bubbling, and the topping reaches a golden-brown hue.

Remove from heat and allow to set for 15 minutes at room temperature to stabilize the fruit pectin before service.