Place onions in a small bowl. Bring vinegars, sugar and salt to a gentle boil, stirring to dissolve sugar. Remove from the heat and add the allspice and red pepper flakes. Pour vinegar mixture over the onions and let cool completely. Store in a jar in the refrigerator until ready to use.
Toast bread until nicely browned. Spread Vegenaise over the toasts. Divide avocado slices between the toast and mash gently with a fork. Season with salt and pepper. Top evenly with tuna, pickled onions, parsley, almonds, and olives.Season again with salt and pepper. Serve right away.
Recipe by My Lilikoi Kitchen at https://www.mylilikoikitchen.com/2018/05/04/avocado-tuna-pickled-red-onion-toast/