Melt butter in a small saucepan over a medium heat. Meanwhile, combine vinegar and egg yolks in a blender or food processor and process until combined.

With motor running, add the hot melted butter to egg yolk mixture in a fine, steady stream, leaving behind the milky residue, to form a smooth, thick sauce.

Add the lemon juice, then process until combined. Remove sauce from blender, season with salt and pepper, cover and set aside.

Trim ends from asparagus; steam or microwave until just tender, drain. Divide asparagus and smoked salmon between 4 serving plates, top each with a dollop of warm hollandaise sauce and season with freshly ground pepper.