Red onion adds a bold hue and sharpness, but you may opt for white, yellow, or sweet onion. To reduce pungency, soak chopped onion in ice water for 10 minutes and drain thoroughly.
For the peas, a quick rinse under cold water speeds up thawing; ensure they are well-drained before layering.
The sugar subtly enhances the mayo, converting it into a sweet-tangy dressing. It can be omitted for a more savory profile.