Heat olive oil in a large skillet over medium heat.
Add diced onion and sauté until translucent, about 5 minutes.
Stir in minced garlic and cook for an additional minute.
Pour in the crushed tomatoes and add the tomato paste.
Season with oregano, basil, salt, and pepper.
Bring the sauce to a simmer and reduce heat to low.
Let the sauce cook for 20-30 minutes, stirring occasionally.
Taste and adjust seasonings as necessary.
Remove from heat and let cool slightly.
Serve over cooked spaghetti and garnish with fresh basil.