Set a dutch oven over medium heat and melt the butter.
Then add the onions, garlic, red chili flakes and oregano. Sauté for about 4-5 minutes until the onions soften and turn translucent.
Then add the tomatoes and turn down the heat to low. Simmer the sauce for about 30-40 minutes, stirring every 10 minutes.
Once the tomatoes are done cooking, let them cool down for about 15 minutes. Then transfer to a blender. Add the mascarpone and blend the sauce until you get a smooth consistency.
Finally, cook your pasta al dente. Reserve a cup of pasta water. Drain your pasta and transfer to pan. Pour the sauce into the pan along with the reserved pasta water. Then toss the pasta and sauce together.
Garnish with fresh basil or parsley and serve immediately.
