Preheat the oven to 350°. In a small bowl, mix together the streusel ingredients with a fork, until it's formed into small crumbs and there aren't any big lumps of coconut oil remaining. Set aside.
In a large bowl, stir together applesauce, plain Greek yogurt, coconut sugar, eggs, and vanilla extract until no lumps of yogurt are remaining.
Add the whole wheat pastry flour, baking powder, baking soda, cinnamon, and nutmeg and stir until combined. Try not to overmix.
Pour batter into a greased 9x9 or 8x11 pan. Sprinkle the streusel topping evenly on top of the batter, then bake for 30-35 minutes, until done all the way through and a toothpick inserted in the center comes out clean.
Allow to cool for 10 minutes, then serve with your favorite cup of coffee or tea!