Prep your pan and oven: Preheat your oven to 350°F and generously grease a 12-cup bundt pan with non-stick cooking spray, making sure to coat all the grooves and center tube.

Mix the apples: In a small bowl, toss together the diced apples, ¼ cup brown sugar, and 1 teaspoon cinnamon until the apples are evenly coated. Set aside.

Create the cinnamon sugar coating: In a large mixing bowl, whisk together the granulated sugar and remaining 2 teaspoons of ground cinnamon. Open both packages of refrigerated biscuits and cut each biscuit into 4 equal pieces using a sharp knife or clean kitchen scissors. Working in batches, toss the biscuit pieces in the cinnamon sugar mixture, ensuring each piece gets completely coated.

Layer the monkey bread: Scatter one-third of the seasoned apple mixture into the bottom of your prepared bundt pan. Top with one-third of the cinnamon sugar-coated biscuit pieces. Repeat these layers two more times, ending with biscuit pieces on top.

Make and pour over the sauce: In a small bowl, stir together the melted butter, 1 cup brown sugar, and vanilla extract until smooth. Pour this rich sauce evenly over the layered biscuits and apples in the bundt pan. No need to mix.

Bake and check: Place the bundt pan in your preheated oven and bake for 50-60 minutes, until the top is golden brown and cooked through. Check the bread at the 45-minute mark - if the top is browning too quickly, tent it with aluminum foil for the remaining baking time.

Cool and serve: Allow the monkey bread to cool in the pan for exactly 10 minutes (this prevents it from falling apart), then carefully invert it onto a serving platter. Serve warm while the sauce is still gooey and the flavors are at their peak.