01 -
Wash 4 to 5 half-pint jars and lids in hot soapy water. Rinse well and keep them warm while you cook the relish.
02 -
Dice the pineapple into small chunks. Slice the jalapenos into thin rounds, removing some seeds and ribs if you want a milder batch.
03 -
Add vinegar, sugar, lemon juice, salt, mustard seed, turmeric, garlic, and ginger to a large stainless steel pot. Bring to a boil over medium-high heat, stirring until the sugar dissolves.
04 -
Reduce the heat and simmer uncovered for 10 minutes, stirring now and then, until the syrup smells spicy and looks clear and glossy.
05 -
Stir in the diced pineapple, jalapenos, and red pepper flakes if using. Simmer gently for 15-18 minutes, until the pineapple is tender and the syrup lightly coats a spoon.
06 -
Spoon the hot mixture into warm clean jars, leaving about 1/2 inch of space at the top. Cool at room temperature, cover, and refrigerate at least 12 hours before serving.