Combine the beef ribs, oil and spice mix together in a large bowl, making sure the spice mixture coats the ribs evenly. Cover and chill for 10 minutes to marinate.
Preheat oven to 200C. Line a baking tray with baking paper. Preheat a pan to moderately low. Use a pan that suits the number of pieces to be cooked. Add the beef ribs and cook for 10 minutes each side. Transfer beef ribs to prepared tray. Bake for 20 minutes until just tender. Remove beef ribs, cover it loosely with foil, and rest in a warm place for 5-10 minutes before serving. Season with salt and pepper.
Meanwhile, mash 3 of the avocado in a large bowl. Chop the remaining avocado and add to the mashed avocado. Add the tomato, green onion, juice, chilli and coriander to mixture. Season with salt and pepper. Stir gently with a fork until just combined.
Serve beef ribs with the guacamole and tortillas.
To score the ribs, use a sharp knife to cut 1cm deep incisions, at 1cm intervals, crosswise down the length of the rib.
If time permits, marinate the ribs overnight. The marinated ribs can also be frozen for up to 2 months before cooking. Simply defrost in the fridge overnight.
To reduce the heat of the chilli simply removed the seeds and white membrane before chopping.
It’s best to make the guacamole just before serving. You can use small basil leaves instead of coriander if desired.