Combine the pawpaw, onion and red capsicum in a bowl. Add the coriander, lime juice, garlic and chilli paste. Toss to combine, then refrigerate until ready to serve.
Preheat a barbecue for high heat and lightly oil grate.
Brush the tuna steaks with olive oil then season with salt and pepper. Whisk the eggs in a shallow bowl until smooth. Dip the tuna steaks in the egg and allow excess egg to run off. Press into the macadamia nuts.
Cook the tuna steaks on the preheated barbecue to your desired degree of doneness. Serve with the pawpaw salsa.