Preheat oven to 350, if using. Mix dry ingredients together (paprika, garlic powder, onion powder, salt and pepper), and spread evenly on the fish.
Place in oven, or air fryer, to cook, flipping halfway through.
Meanwhile, warm skillet and melt butter and olive oil. Add finely chopped shallots and garlic. Don't overcook-just enough to get fragrant but not browned.
Add chopped asparagus, crushed red pepper, salt and pepper. Stir well to coat and cook until asparagus becomes fairly tender.
Add the stock and lid, allowing to simmer a bit and tenderize. Adjust amount of stock/water to keep liquid in the pan (about 1/4 inch).
Transfer contents of skillet to mixing bowl (for technique, you could use a tall stock pot and avoid the transfer if cooking a larger quantity). Using immersion blender, carefully puree until smooth, adjusting salt and pepper to taste.
Keep puree warm, and when fish is cooked through, plate a large serving of puree with the fish fillets. Served with crushed pistachios to garnish. Enjoy!