Preheat the oven to 425 degrees F. Position a rack in the top third of the oven. Place the asparagus on a baking sheet lined with parchment paper. Drizzle with the olive oil and sprinkle lightly with salt and pepper. Roast until tender, about 15 minutes.
Meanwhile, combine 5 tablespoons of the almonds, the lemon juice, sugar and 6 tablespoons water in a blender and blend until smooth, about 1 minute. Taste the sauce and season with salt. Pour the sauce onto a platter and place the asparagus on top. Garnish with the zest and remaining 1 tablespoon almonds.