Preheat the oven to 375 degrees F.
Cut spaghetti squash in half lengthwise and dig out the seeds. You can pop it in the microwave for 5-10 minutes to make it easier to cut.
Place each squash half facing downwards in a baking dish and bake for 35-45 minutes, depending on the size of the squash. The spaghetti squash strands should be easy to fluff with a fork.
Meanwhile, prepare the shredded chicken using your favourite method. I like to boil the chicken breasts for about 20 minutes, but you can also prepare it in an instant pot, slow cooker or use a rotisserie chicken.
Combine all of the ingredients for the pesto in a food processor and blend until mostly smooth. Alternatively, you can sub in store-bought pesto if desired.
Toss the pesto with the shredded chicken and gently fold in the halved cherry tomatoes.
Once the spaghetti squash is cooked, fluff it up using a fork, making sure that you scrape the strands off the sides of the squash. Sprinkle some salt and pepper on each half.
Evenly distribute the chicken pesto mixture across each half, making sure that you fold the chicken mixture in with the spaghetti squash strands. Top with a sprinkle of cheese, if desired.
Place in oven and bake for 20 minutes or until warmed through.