Preheat your oven to 325°F.
Lightly grease a 10-inch glass pie plate so the cake pops out easily after baking.
In a medium bowl, toss cranberries, diced apple, brown sugar, orange zest, orange juice, and 1 teaspoon of cinnamon until the fruit gets coated evenly.
Beat the eggs on medium-high for about 2 minutes until they're a bit thick.
Add 1 cup granulated sugar, melted butter, vanilla, and sour cream, mixing just until everything comes together.
Add the flour and salt on low speed and mix until you see no dry streaks.
Overmixing makes the cake dense, so hold back.
Spread the fruit mixture in your prepared pie plate.
Pour the batter over and gently smooth it to cover the fruit.
Mix the last tablespoon of granulated sugar with 1/8 teaspoon cinnamon and sprinkle over the batter for a crisp finish.
Bake for 55 to 60 minutes.
When a toothpick in the center comes out clean and the fruit bubbles at the edges, it's done.