Bring about 3-4 quarts of water to a boil and cook the penne with a dash of salt until fully cooked. 

Drain pasta and add butter. Mix well and add salt and pepper to taste. 

Slice mushrooms. 

Drizzle a teaspoon of oil on a large pan and bring to medium heat. Add the sliced mushrooms and stir occasionally on medium/high heat until the mushrooms are browned and reduced in size (the mushrooms will produce a lot of liquid, but add another tsp of oil to cook them if necessary). Add the spinach and stir until it begins to wilt. 

Cut the tomatoes in half or keep whole and add to the pan (whole tomatoes will need a bit more time to cook so add them earlier). Once the tomatoes wrinkle and the spinach is wilted, turn of the flame. 

Place the pasta in a serving bowl and add the vegetables on top. Lightly mix. Garnish with parmesan cheese, and keep more cheese on the table, of course!