Preheat your oven to 350 degrees.
Cut the squash into 1/4-inch slices and dice the onion.
In a dutch oven or stock pot, saute the squash in avocado oil spray over medium heat until soft, about 5-7 minutes.
Remove the squash from the dutch oven and let it sit in a colander for a bit to remove some of the excess liquid. Use the back of a spoon to gently press on the squash to help things along if you'd like.
While the squash is resting, deglaze the dutch oven with chicken or vegetable stock.
Add the onion and saute until soft and translucent, about 3-5 minutes.
Turn off the heat and add the garlic, salt, and pepper. Stir to combine.
In a large bowl, combine the squash and onions with the sour cream, Greek yogurt, half of the panko, and half of the shredded cheese.
Spread the mixture in a sprayed 9x13 baking dish and top with the remaining shredded cheese and panko.
Bake at 350 degrees for 20-25 minutes until the cheese has melted and the panko has started to brown.