Preheat your oven to 375°F (190°C).
Core and chop the Honeycrisp apple into bite-sized pieces.
Heat the coconut oil in a small skillet over medium heat, then add the chopped apples, water, ground cinnamon, and sea salt.
Sauté the apples for 5-7 minutes, stirring occasionally, until they are tender and the liquid has reduced into a light syrup.
In a small mixing bowl, combine the rolled oats and chopped walnuts.
Transfer the sautéed apples into a small oven-safe ramekin or baking dish and sprinkle the oat-nut mixture evenly over the top.
Bake for 10-12 minutes until the topping is golden brown and fragrant.
While the crumble is baking, whisk together the nonfat Greek yogurt, vanilla protein powder, and vanilla extract in a bowl until completely smooth.
Spoon the warm apple crumble directly over the cold yogurt base and serve immediately.