1 red onion, finely diced
15 whole black peppercorns
15 whole allspice berries
4 bay leaves
1/3 cup juice from 1 grapefruit (2 1/2 ounces; 80ml) (see note)
1/3 cup juice from 1 to 2 oranges (2 1/2 ounces; 80ml) (see note)
1/3 cup juice from 4 to 5 limes (2 1/2 ounces; 80ml) (see note), plus a little extra just in case
Salt
Place onion, peppercorns, allspice, and bay leaves in a small saucepan and cover with water. Bring to a boil over high heat. Remove from heat, drain carefully, and transfer onions to a sealable container, such as a Mason jar.
Add grapefruit, orange, and lime juice. Onions should be submerged at this point; if they aren't, top off with extra lime juice. Stir to combine, season to taste with salt (they should be quite salty—use about 1 teaspoon of kosher salt or 1/2 teaspoon of table salt), cover, and refrigerate until color deepens, about 2 hours. Onions can be stored in the refrigerator for up to 2 weeks. Do not eat peppercorns, allspice berries, or bay leaves.
➤ (the lobster made this for us and it was delicious!)