Peel the lower half of the asparagus spears with a peeler and cut diagonally into 4 pieces. Cut the onion into wedges by slicing it into 8 sections.

Season the scallops with a pinch of salt and pepper, then coat them lightly with all-purpose flour.

Heat butter in a frying pan over medium heat. Add the scallops and cook for 1–2 minutes on each side until golden brown, then remove them from the pan. Add asparagus and onion to the pan, stir until coated with oil, cover, and steam on low heat until the onion becomes translucent.