Remove the scallops from their shells (steps 3–4, opposite), discarding the roe. Clean and dry 4 shells and keep for serving.
Line a steamer with baking paper and place the scallops on top. Steam for 1–2 minutes. Reserve four of the scallops, and finely chop the remaining scallops.
Put the avocado, capsicum, tomato and onion in a bowl, t