In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes, until translucent.
Stir in the minced garlic and cook for an additional 1-2 minutes until fragrant.
Pour in the crushed tomatoes, and add the oregano, basil, red pepper flakes (if using), sugar, salt, and pepper. Stir well to combine.
Bring the sauce to a simmer and let it cook for 15-20 minutes, stirring occasionally, until it thickens slightly.
Reduce the heat to low and add the softened cream cheese, stirring until fully melted and incorporated into the sauce.
Remove from heat and stir in the grated Parmesan cheese. Adjust seasoning if necessary.
Serve over your favorite pasta and garnish with fresh basil leaves if desired.