Step 1Preheat oven to 210°C. Line a large baking tray with baking paper.
Step 2Place sweet potato on prepared baking tray. Spray with olive oil and sprinkle with 3 teaspoons of the fajita spice mix. Bake potatoes for 25–30 minutes, or until tender, tossing halfway during cooking.
Step 3Meanwhile, squeeze any excess liquid from the grated onion and place into a large bowl. Add beef mince, 1 tablespoon of remaining spice mix and garlic. Mix well until thoroughly combined. Divide the mixture into 4 equal portions and shape into 10cm patties.
Step 4Spray a large non-stick frying pan with olive oil and set over medium heat. Add the patties to the pan and reduce heat to low. Cook for 8–10 minutes, turning once, or until cooked through.
Step 5Mash half of the kidney beans. Divide the sweet potato wedges between 4 serving plates and top with beans, tomato slices, beetroot and burger patties. Top the patties with baby rocket and serve with a little tomato salsa on the side, if preferred.