Get Your Cook On
1) Put a pan of water on and bring it to the boil, adding salt if you have it.
2) Whilst this is happening gently fry your sausages in the frying pan. Keep an eye on them, you want them lightly coloured all over, but not incinerated.
3) Slice the onion.
4) Once the sausages have browned, remove them from the pan and chop into slices. You want it fairly thin, say 8 slices per sausage.
5) Return the sausages to the pan with the onion, and cook them some more. You want the onion translucent (ie softened) rather than caramalised (ie brown).
6) Add the tinned tomatoes to the frying pan with the sausages and onion, and make sure they're all squidged up. Bring it to a light simmer. Add the pasta to the now-boiling water. Set a timer for about 10 minutes.
7) At this point season the sauce with black pepper, and if you're using dried basil you can add it at now as well. Always leave fresh basil until the end.
8) Once the timer goes off, try some of the pasta to make sure it is cooked to your liking. If it isn't leave it in a bit longer.
9) Drain the pasta when ready, and then add it back to the saucepan you cooked it in.
10) If you're using fresh basil, tear the leaves up and stir them into the sauce now.
11) Add the sauce to the pasta in the pan and mix it all up. You can add a dash of olive oil at this point if it pleases you.
12) Serve in bowls. Top with cheese if you want to. Eat. Nap.
Summary
If you are just cooking this for one, halve the amount of pasta you cook (You need 130g-150g per person, which is between a quarter and a third of a 500g bag).
You can save half of the pasta sauce for another time, and cook more pasta fresh when you need it. Pasta is not great re-heated.