Cook the pasta according to package directions.
While pasta cooks, heat 1 tablespoon olive oil in a large skillet. Add onion, and sauté over medium-high heat until tender and fragrant, about 3 minutes. Add salt, balsamic vinegar, sun-dried tomatoes, crushed red pepper, and pine nuts; cook, partially covered, over medium-low heat for 4 minutes, stirring occasionally.
When al dente, drain the pasta and add it to the skillet, stirring to combine for about 1 minute. Transfer the pasta to a large serving bowl, and toss in the feta cheese, basil, and remaining olive oil. Serve immediately.
We use only fresh rigatoni from the local Italian shop and the dish is fantastic.