Wash the sweet potato well and prick it all over with a fork. Wrap it in two sheets of damp kitchen paper and place on a microwave-safe plate. Microwave on high for 6 minutes, then continue cooking in 1-minute intervals until tender. Mine took 8 minutes. Carefully slice it open and fluff the inside with a fork.
While the potato is cooking, heat the olive oil in a frying pan over medium-high heat. Add the beef mince and cook for 5–6 minutes, breaking it up with a spoon until browned. Stir in the fajita seasoning and cook for another minute.
In a small bowl, combine the cherry tomatoes, coriander, red onion, jalapeño, olive oil, salt and black pepper.
Sprinkle the grated cheddar inside the hot sweet potato and allow it to melt slightly. Top with the cooked beef, spoon over the fresh salsa and finish with the sliced avocado. Serve immediately.