Preheat the oven to 400 degrees.
Put 1 tablespoon of olive oil in the bottom of a casserole dish. Butterfly the chicken breasts (cut in half length-wise) and place them flat in the dish.
Next, surround the chicken with cherry tomatoes, onions and garlic.
Spoon out the cream cheese around the dish so you have about 1 inch around dollups of cream cheese evenly spaced. I like to put mostly on the chicken so I know it won't burn to the bottom.
Season everything in the casserole dish with salt, pepper, and Italian seasoning.
Place the casserole dish in the oven for 20 minutes or until the chicken reaches a tempurature of 165 degrees.
While the chicken is cooking, cook the spaghetti squash. My favorite way to do this is cut it in half on the equator, scoop the seeds out, and microwave it in five minute increments until it's done. This typically takes about 15 minutes. You can also cut it the same way, remove the seeds, and cookit in your Instant Pot for 13 minutes.
When the spaghetti squash is cooked, use a fork to scrape out all the "meat" of the squash.
When the chicken is done, shred the chicken and mix the cream cheese (should be soft), tomatoes, and chicken together. Add in the squash and combine until it is coated in the sauce.
Add extra basil on top and enjoy!