Bring a large pot of water to a boil. Add 1 tablespoon of salt to the water. Then add the pasta and cook according to directions (about 8 - 10 minutes). Reserve about 3/4 cup of the salted pasta water in a heat-resistant container like a tempered glass measuring cup, then drain the pasta. Set the pasta and reserved pasta water aside briefly.
While pasta cooks, heat a large saute pan over medium. Add in the olive oil. When the oil is hot (but don't let it start smoking), add the mushrooms and diced pepper to the pan, cooking until the mushrooms give up their juices, browning a bit, and the pepper is softened. Add the dried oregano, if using, and cook for another 30 seconds.
Add all the tomatoes into the pan with the mushrooms and pepper. Cook for about 6-8 minutes. The tomatoes should look a bit crinkled and begin to pop open. Slight pressure on the tomatoes with the back of a spoon helps them to break down.
Now add in the sliced garlic and cook for a couple more minutes.
Stir in the pesto ( or sliced fresh basil leaves) and take the pan off the heat.
Add the salted pasta water, starting with one tablespoon at a time, to achieve a more saucy recipe that combines well with the pasta. (You probably won't need all of it). This step is optional.
Return the pasta to the pasta pot. Stir the tomato and veggie sauce into the pasta. Sprinkle with a couple tablespoons of vegan parmesan, if using.
Sprinkle with salt and pepper to taste.