If using a Ninja or similar combination pressure cooker / air fryer, melt the butter on the sear setting. Otherwise, do this in a large pot on the stovetop.
Add garlic to butter and cook until soft. Whisk the tomato paste into the water.
Whisk in the flour to create a paste, then whisk in the tomato paste water until well combined.
Add the chopped squash, bell pepper, carrots and spinach. Stir to combine.
Add turmeric, basil and chili powder. Mix.
If using a Ninja or something similar, switch to pressure cook, attach pressure lid, and cook on high for 1 hour and release pressure (allowing it to release on it's on is fine too). If cooking on the stove top, cook on medium heat for two hours.
Transfer soup to a large bowl and using an immersion blender, blend the soup to your preferred thickness. *Using an immersion blender directly in your pot or pressure cooker liner can scratch and damage it.