800gm hand-mashed whole canned peeled tomatoes
3 Tbsp. olive oil and a little more for serving
4 finely chopped garlic cloves
1 diced small onion
1 tsp. dried oregano
Chopped fresh basil
2 tablespoons diced unsalted butter
In a large skillet, combine olive oil and garlic. Cook over medium heat until garlic is golden around the edges, about 3 minutes. Add onion, oregano and 1 tsp. salt. Cook, stirring, until onions are soft (but don't let them brown), about 10 minutes.
Add the tomatoes and their juices and 0.5 tbsp. water; continue cooking until the sauce has reduced in volume slightly, about 20 min. Stir in the basil and season with salt. Keep the sauce warm over low heat.Meanwhile, in a large saucepan, bring the salted water to a boil. Add the pasta and cook according to the instructions on the package. Save 1 tbsp of the water in which the pasta was cooked, drain the rest of the water.
Add the pasta, 0.5 tbsp of the water it was cooked in and the butter to the sauce. Increase the heat to medium and stir, adding the remaining cooking water from the pasta if you need to thin out a too thick sauce. Spread the spaghetti and marinara sauce into bowls and drizzle with olive oil.