For stuffing, heat butter in a frying pan over high heat; cook bacon, garlic, shallots and lemon myrtle, stirring occasionally until shallots soften (6 minutes). Transfer to a large bowl with breadcrumbs, macadamias, cranberries, herbs, parmesan, zest and oil. Season to taste and mix to combine.
Preheat oven to 180°C fan-forced. Place pork lengthways in front of you on a chopping board, run a knife parallel to and up against each rib, cutting down into the thickest part of the meat and finishing the cut 2cm from the bottom. Rotate knife so the blade is horizontal, continue slicing along the length of the meat maintaining a 2cm thickness and unrolling the meat as you cut, keeping meat attached to ribs. Open out to form one large piece, then scatter with extra lemon myrtle. Spoon stuffing into centre of pork and season to taste. Fold pork back toward ribs, then using kitchen string tie in between each rib to secure.
Place pork on a wire rack over a deep oven tray. Drizzle with oil and season to taste. Roast until golden and meat is cooked through (1 hour 20 minutes). Rest loosely covered with foil for 20 minutes; then carve and serve.