Pasta with Lemony Herb Sauce

I love to fix this quick and easy pasta dish for my family.  You can add shrimp or chicken if you want, but it's delicious on its own without meat.  I adapted the recipe from Food Network to meet our gluten-free needs.

6 T. olive oil

1 medium yellow onion, thinly sliced

Salt and freshly ground pepper to taste

1/2 cup chopped fresh green onions

1/4 cup finely chopped fresh parsley

1/4 cup chopped fresh tarragon

2 (8-oz.) boxes of gluten-free pasta (spaghetti or fettuccine)

2 t. lemon zest 

1. Cook the pasta according to package instructions and drain, reserving 1 1/2 cups of pasta water.
2. Meanwhile, heat 2 T. of the oil in a large frying pan over medium-high heat.  Once simmering, add the onion and season with salt and pepper; cook, stirring continuously.  It will take about 5 minutes for the mixture to get soft and translucent.  Remove from heat and stir in half of the fresh herbs. 
3. Return the (empty) pasta pot to the stove.  Add the onion mixture, the rest of the olive oil, the rest of the herbs, the reserved pasta water and lemon zest.  Season with salt and pepper, stir, add the pasta and toss to coat.  
4. Top with Parmesan cheese and parsley sprigs before serving.