To make the black beans, put the drained beans in a blender with the fajita spice mix and a pinch of salt and pulse until well mixed. Scoop out onto a plate and spread evenly.
Next, mash the avocado with the squeeze of lemon and a sprinkle of salt and put on top of the black beans.
To make the salsa, put the tomato halves in a bowl and add the remaining salsa ingredients. Toss gently.
Put a dollop of salsa on the plates, scatter the corn chips around the edges and add some lime wedges for extra zing. Enjoy straightaway.