Add in tomato puree and mushrooms. Season with black pepper. By now the water should be boiling so get the pasta cooking as well.
  
 
Step 3:

After a few minutes of simmering, everything should be starting to look delicious. At this point I decided to add some chili powder, the black pepper just wasn't doing it on its own.
 
Step 4:

Everything should be ready to eat by the time the pasta is done. As with most anything though, simmering longer only makes the flavor better, so you might start the pasta later on in the process if you have time. I like olives, so I added some pepper stuffed ones on the side.