In a large skillet or Dutch oven, heat olive oil over medium-low heat.

Add the chopped onion and sauté until softened, about 5 minutes.

Stir in the minced garlic and cook for another minute until fragrant.

Add diced tomatoes, tomato paste, and a pinch of sugar, stirring to combine.

Bring the sauce to a boil, then reduce heat to simmer gently for about 20 minutes, stirring occasionally.

Meanwhile, cook penne pasta in salted boiling water according to package instructions until al dente.

Drain the pasta and reserve 1 cup of pasta water.

Combine the penne with the sauce, tossing to coat. Add reserved pasta water if the sauce is too thick.

Serve immediately, garnished with grated Parmesan and fresh basil leaves, if desired.