Prepare spaghetti squash: cut in half, scoop out seeds, put face down in baking pan with 1/4 cup of water in the pan. Bake at 375 degrees fahrenheit for 35-40 minutes, depending on size of squash. While baking, prepare other ingredients below. Shred with a fork into a bowl.
Finely chop the fresh basil and garlic. Add a pinch of salt and pepper, then add the olive oil. Mix thoroughly into a pesto.
Slice grape tomatoes in half.
Cube cooked chicken breast.
Mix spaghetti squash, pesto, grape tomatoes, and chicken breast in a pot on the stove, and bring to an even temperature (about 3-5 minutes). It's easiest if you pre-warm the chicken breast as it takes the longest to heat.
Split into 2 servings and top with shredded parmesan if desired.