The technique known as ribboning is the way to perfect cake-making. When your egg batter forms a ribbon when dropped from lifted beaters, then it's exactly right. The batter should drop in a wide, flat band that folds in on itself. If it falls in thin straight lines without folding in, keep beating.
Ribboning ensures both that the sugar is completely dissolved and that the eggs are well aerated and evenly dispersed. For this reason, it's always preferable to use a mixer rather than a food processor for cake batters.