Preheat oven to 425°

Spread the tomatoes out on a cookie sheet and drizzle 2 tablespoons of olive oil on top, covering all of the tomatoes.  Put in oven for 30 minutes or until the tomatoes start to brown.

In the meantime, heat up the remaining 2 tablespoons of olive oil in a skillet and cook the onions and mushrooms until soft.  Season with salt and pepper to taste.  The salt will help with the water that naturally comes from the mushrooms.  Add the garlic for the remaining 30 seconds.

In another pot, follow instructions to cook your pasta.  If you don't have flavored pasta handy, you can use whatever you do have.

Add the pasta to the skillet with the onions, mushrooms, and garlic.  Cut the lemon in half and add the juice of the entire lemon to the pasta mixture.  

When you are ready to serve, add the tomatoes to the top and sprinkle some fresh parmesan on top.