You will need:
Pasta, cooked - preferably shapes, not long, thin or flat stuff, about 50-75g per person, depending on appetites ;-)
Chorizo - half a "ring" is more than enough for two people.
One tin of chopped tomatoes
Sweetcorn, fresh or frozen
Fresh tomatoes - some for the garnish
Mozzarella cheese (you can substitute any sort of cheese really)
First of all, chop the chorizo into smallish pieces. Add this to a pan over a medium heat - you don't need oil as the chorizo has plenty within. The chorizo will also release the garlic and paprika flavours that will flavour the whole dish.
Finely chop the onion and add it to the chorizo, keeping the heat at a medium level. Slowly allow the onion to soften; it will absorb some of the oil and the flavouring.