Melt butter in a saucepan; sauté onion, garlic, celery seeds and chili flakes until onion is translucent. Add sugar, raisins and pineapple. Cook over medium-high heat until pan is nearly dry and sugar starts to caramelize. Add vinegar and swirl the pan vigorously to thoroughly mix. Cook until mixture is nearly dry again and season to taste.

Using a wide-mouth funnel, ladle the mixture into the sterile jars (see prep steps on p. 99), filling to 1/2" from the top. Using a paper towel dipped in boiling water, carefully wipe jar rims clean of any preserve mixture. Any residue will prevent a proper seal. Using a magnetic lid lifter, lift the lids onto the jars and place a ring over the top. Tighten the rings “finger-tight” only. Lower the filled jars onto the rack in the pot of boiling water. The jars should be covered by at least 1" of water. Put the lid on the canner and once the water returns to a boil, set a timer for 15 minutes.

After 15 minutes, carefully remove the jars using a jar lifter (special tongs made for lifting jars), being careful not to tip them over. Place them on a rack to cool, undisturbed, overnight. Next day, you can remove the rings (or tighten them a little and leave them on) and store your preserves. Makes 1-2 (250 ml) jars.