Pink Sauce Pasta

0 Bring a pot of water to the boil, add the pasta, and cook as directed on the packaging.
1 In a separate pot, heat the oil and sauté the onion until soft, 2-3 minutes.
2 Add the garlic and continue to sauté for another minute.
3 Next, stir through the diced tomatoes, marinara sauce, oregano, dried red pepper flakes, torn basil leaves, salt, and pepper.
4 Reduce heat and gently simmer while stirring. Adjust seasoning to taste. Add sour cream and stir through. (Optional: for a smoother sauce, puree with an immersion blender).
5 When the pasta is just cooked, strain it and mix through the sauce. Continue to cook for another 3-4 minutes while stirring.
6 Stir through ½ of the grated parmesan cheese if using. 
7 Serve hot with remaining grated parmesan cheese.