Spinach pesto chicken pasta

We had some friends over for dinner and made a quick pesto chicken pasta, using ingredients from my definitively favorite store: Costco!  I included a package of frozen spinach and it added a good flavor while boosting the veggie content.

Spinach Pesto Chicken Pasta
6 servings

1 lb pasta (preferably short-cut pasta like rotini, farfalle or penne)
1 10oz. bag frozen chopped spinach
1/2 white or brown onion, diced
2.5 cups grape tomatoes, quartered
2 cups shredded chicken (we used Costco rotisserie chicken)
1/3 cup pesto sauce (homemade or from Costco)
Salt and pepper, to taste

1. Cook frozen spinach according to the directions on the package.  Drain spinach and set aside.  In a saucepan on medium-high heat, saute the diced onions until soft and translucent.  Add spinach and grape tomatoes, stirring occasionally for 5 minutes and then remove from heat.
2. Bring a large pot of water to boil and cook pasta until al dente, according to the directions on the package. When draining the pasta, reserve 1 cup of the pasta liquid.  Rinse pasta with cold water to stop cooking and return pasta to the large pot.
3. Stir the spinach, tomatoes and onions into the pasta.  Add shredded chicken and pesto sauce and stir to combine.  If the pasta is too dry, add some of the reserved pasta liquid until desired consistency.  Add salt and pepper to taste.  Serve warm.