The jalapeños themselves lend a spicy kick while the brine provides tang to offset the savory tuna and rich avocado. The brine also quick-pickles the red onion, which tames its raw bite.

Another option when purchasing canned tuna is for the fish to be packed in brine. Though not as popular a choice, you may still see brine-based canned tuna on the supermarket shelves. Brine is ...