12ouncesbutton or Cremini mushrooms,washed and sliced or left whole * see notes
2cupsdiced tomatoes,canned or fresh (either works fine)
1/4cupParmesan cheese,grated (optional for topping)
1tablespoonfresh parsley,chopped (optional for topping)
Bring a large pot of salted water to a boil. Add in your spaghetti and cook according to the package instructions. Reserve 1 cup of pasta water for the sauce. Drain and set aside the spaghetti.
In a large skillet, combine olive oil and your diced onion. Place the skillet over medium heat and cook for about 3 to 4 minutes, or until the onion softens and turns translucent.
Crank the heat up slightly to medium-high, and add in the mushrooms. Sauté for 5 minutes, or until softened and golden brown. They also shouldn't be releasing as much liquid.
Add your oregano and tomatoes. Cook for another 5 to 10 minutes, or until the tomatoes have broken down and softened. If the sauce seems too dry, add a splash of the reserved pasta water to get it to your desired consistency. Add the garlic in at the end and let it cook for an additional minute.
Plate your spaghetti and top with the mushroom sauce! Serve with your favorite toppings (I always go with Parmesan and chopped parsley).
* I like to leave my mushrooms whole for added oomph! You can also slice your mushrooms, but they'll cook much quicker (a plus!), so keep an eye out for the cook time.