Score each tomato with an X on the bottom. Drop tomatoes into a large pot of boiling water for 30 seconds to 1 minute. Using a ladle, transfer tomatoes from boiling water into a large bowl of ice water. Remove tomatoes from the water into a separate bowl; allow to cool 1 to 2 minutes. When you can handle tomatoes with your hands, gently rub the skins off of the tomatoes. Cut into wedges and remove the seeds.
Add tomatoes, garlic, onion, salt, red pepper flakes and paprika to a large pot. Cook over medium-high heat, stirring occasionally; bring to a boil. Add sugar and pectin, then bring back to a boil; cook additional 5 minutes or until sugar is dissolved. Remove pot from heat.
SHORT-TERM STORAGE:
Fill warm sterilized jars with tomato relish to the top of the jar. Wipe rims clean, seal with lids and rings. Store jars in refrigerator for up to 1 week.
LONG-TERM STORAGE:
Fill warm sterilized jars with tomato relish, leaving a 1/4-inch space at the top. Wipe rims clean, seal with lids and rings. Using tongs, place the jars into a hot water bath; be sure that the jars do not touch one another, and are fully submerged. Cover the pot with the lid, heat water to a slow boil for about 10 to 15 minutes. Use tongs to remove jars from pot. Allow to cool.
Check seal after 12 to 24 hours. Store for up to 1 year in a cool, dry storage place.
