To make onions less strong, here are some effective methods:

• Soak them in ice cold water for about 10-15 minutes. This reduces the sulfur compounds that make onions pungent, while keeping them crunchy.
• Coat them in salt and let sit for 15 minutes, then rinse off. Salt draws out moisture and some of the strong compounds, softening their bite.
• Soak in vinegar or citrus juice to mellow flavor and add a tangy note.
• Quickly microwave with a bit of water or vinegar for about 10 seconds to reduce sharpness while retaining texture.
• Pickling or marinating onions in vinaigrette also softens pungency.

Cold water soaking is the most common and easiest method used in restaurants to tame raw onion's sharpness without cooking them. These methods preserve onion flavor but reduce the harsh bite and lingering aftertaste.