Heat the olive oil and butter in a medium saucepan over medium heat.
Add the onion and cook for 4–5 minutes until softened.
Stir in the garlic and cook for 30 seconds until fragrant.
Add the tomato paste and cook for 1 minute, stirring constantly.
Pour in the crushed tomatoes and stir well.
Add the Italian seasoning, basil, salt, black pepper, and red pepper flakes.
Simmer for 10–12 minutes, stirring occasionally.
Reduce the heat to low and slowly stir in the heavy cream until the sauce turns a smooth pink color.
Add the Parmesan cheese and stir until completely melted.
Taste and add the sugar if needed to balance the acidity.
Remove from the heat and let the sauce rest for 5 minutes before serving.
Garnish with fresh basil or parsley and serve over your favorite pasta.