Oven at 350 degrees.
Lets start with the sautéed cinnamon apples. In a pan stir together the apples, 1/2 stick butter, 1 Tbsp cinnamon, vanilla, orange juice, nutmeg, 1/4 cup brown sugar and a pinch of salt. Cook on medium until the apples have started to soften. About 5 minutes. Stir in the water and let it simmer for another 5 minutes, the liquid part will have thickened slightly. Allow the mixture to cool completely.
While the apples are cooling you can go ahead and start putting together the brown sugar crumb topping. This isn't a very crumbly topping, it has a slightly gooeyness too it and its fabulous! Into a food processor pulse the flour, 1 cup brown sugar, 1 1/4 stick softened butter and 2 tsp cinnamon. The consistency you are looking for is somewhere between crumbly and sticky (boy do I hope that makes sense to you). Lets be honest, either way it will taste delish, the texture may differ slightly, no big deal!
Now for the cake. In a bowl, add the Funfetti cake mix, eggs and the cooled apple mixture. Mix until well combined. Pour the cake into a buttered 8x8 pan. Top with the crumble and bake for 35-45 minutes.
The crumble topping will be slightly browned and a toothpick should come out clean when poked through. Once the cake is cooled, sprinkle with powdered sugar.