Preheat Oven: Preheat your oven to 375 degrees F (190 degrees C). Generously coat a bundt pan with cooking spray to prevent sticking.

Prepare Biscuit Mixture: Open the cans of refrigerated biscuits and cut each biscuit into quarters. In a large bowl, combine the quartered biscuit pieces, shredded mozzarella cheese, quartered pepperoni slices, grated Parmesan cheese, Italian seasoning, and garlic powder. Toss the mixture until the biscuit pieces are well-coated with the cheese and seasonings.

Add Butter: Gradually pour the melted butter over the biscuit mixture, gently mixing with your hands or a spoon to ensure even distribution.

Transfer to Pan: Once everything is combined, transfer the biscuit mixture into the prepared bundt pan, arranging it evenly.

Bake: Bake in the preheated oven for 25 to 30 minutes, or until the top is golden brown and the center is cooked through. To avoid over-browning, you can cover the pan with aluminum foil if necessary during the last few minutes of baking.

Cool and Serve: Carefully remove the bundt pan from the oven and let it cool for about 10 minutes. Then, invert the monkey bread onto a serving plate.

Prepare Marinara Sauce: Heat the marinara sauce in a microwave-safe bowl or a small pot on the stove until warm, then serve it alongside the monkey bread for dipping.