Preheat oven to 425 degrees.
In a large bowl, add sliced peaches, lemon juice, cornstarch, brown sugar, white sugar, vanilla, and cinnamon. Gently toss to combine. Pour peach mixture into skillet or 2-quart baking dish. Bake in oven for 10 minutes.
While peaches are baking make the crumb topping.
In a small mixing bowl, combine the 2 tablespoons sugar & 3/4 teaspoon cinnamon. Stir to combine and set aside.
In a medium mixing bowl, combine the remaining crumb topping ingredients: yellow cake mix, brown sugar, salt, and baking powder. Stir to combine. Add butter, and using a pastry blender or a fork, cut butter into the mixture until it resembles coarse crumbs.
Once the peaches are done cooking, remove from oven and sprinkle to your taste the cinnamon and sugar. Then add the crumb topping to cover the peaches entirely. Set back in the oven and bake for 25-30 minutes or until crumb topping is a nice golden brown.
Serve immediately. It’s great with vanilla ice cream or whipped topping.