Use a high-speed food processor or blender with the metal blade attached. Add the Tarama roe, the lemon juice and zest and the graded onion and blend.
Slowly pour in the oil in the same way that you would add it in a mayonnaise recipe process, until you reach a nice light mousse texture. Press Link for Video
Refrigerate for minimum 3 hours for the flavours to come together and to have a smoother/lighter taste of the onion.