Preheat oven to 350°F. Grease and flour a Bundt pan.
In a large bowl, whisk together cake mix, apple cider, applesauce, sour cream, eggs, melted butter, and vanilla until smooth.
Toss diced apple with 1 teaspoon flour, then fold into the batter.
Pour batter evenly into prepared Bundt pan.
Bake 35–40 minutes, or until a toothpick inserted comes out clean.
Let cake cool for 10 minutes, then carefully invert onto a wire rack.
While still warm, brush melted butter all over the cake.
Mix granulated sugar, brown sugar, and cinnamon together. Sprinkle (or roll) the cake until fully coated.
Slice and serve warm or at room temp — perfect with a cup of cider! 🍏