Preheat oven to 450 degrees. Toss the asparagus, garlic and onion with olive oil to coat. Spread them out on a baking pan and roast until the asparagus is very tender. If anything is browning too quickly, take it out. While the asparagus is roasting, blend 1/2 cup of the stock with the cashews or cashew butter and pepper until smooth. Combine all ingredients except the orange peel in a food processor and puree. Add more cashews or cashew butter if needed to achieve desired texture. Serve warm with a sprinkling of orange or lemon zest.