Preheat the oven to 400° F. Carefully poke small holes around the spaghetti squash with a sharp knife and microwave for 5 minutes. Slice the spaghetti squash in half, lengthwise, season with salt and pepper, and place it flesh side down on a rimmed baking sheet flesh with 1/4 cup of water. Roast for 45-60 minutes or until the squash strands are easy to pull apart with a fork. When the squash is ready, pull at the strands with a fork.
About 10 minutes before the squash is finished, heat a pan over medium-high heat with 1/2 cup of BBQ Sauce on med-high heat. Add shrimp and cook for 3-4 minutes on each side.
To serve, divide the shrimp between each spaghetti squash boat and top with smashed avocado, mango salsa, pickled onions, and cilantro.
Notes
If you don't want to make your own Whole30 BBQ sauce, this one is great.