Lightly coat an 8×8-inch baking dish with nonstick cooking spray.

Heat the olive oil in a large skillet over medium heat.

Add the minced garlic and cook for 30 seconds, stirring constantly.

Add the spinach and cook for 2 minutes, stirring occasionally.

Remove the skillet from the heat.

Place the softened cream cheese, sour cream, and mayonnaise in a medium mixing bowl. Stir until smooth.

Add ¾ cup mozzarella cheese, ¼ cup Parmesan cheese, onion powder, salt, black pepper, and optional red pepper flakes. Stir until combined.

Add the cooked spinach and garlic to the cream cheese mixture. Stir until evenly mixed.

Transfer the spinach mixture to the prepared baking dish and spread it into an even layer.

Sprinkle the remaining ¼ cup mozzarella and ¼ cup Parmesan cheese over the top.

Bake for 20 to 25 minutes, until the dip is hot, bubbling around the edges, and lightly golden on top.

Let the dip rest for 5 minutes before serving.