Cook the Barilla spaghetti noodles according to the package
Cook up the chicken breast however you'd like. I usually do mine in a frying pan. Sometimes I'll opt to grill it to give it more flavor.
Once the pasta is done cooking, drain it and put the pasta in a casserole dish. Make sure this dish can be used in the oven.
Now mix up the pesto sauce with the noodles.
Add in the onion and garlic powder and mix well.
Either cut up the chicken in small pieces or shred it and add it to the pasta.
Sprinkle with cheese on top.
Now thinly slice up the tomatoes and lay them on top. You can put as many as you'd like on top, but I try not to add to many.
Now it's ready to cook at 400° for 20 minutes or until all the cheese has melted.
