Measure the tomato purée exactly into a heavy-bottomed pot. Stir juice, lemon juice, vinegar, sugar, and a pinch of salt into the pot.
Bring mixture to a rolling boil over high heat and allow to boil for one minute, stirring constantly!
Remove from heat and add pectin. Bring to a boil for one minute. Bring the temperature up to 220 degrees (candy stage).
Quickly ladle into prepared jars, leaving 1/8 inch of headspace. Wipe jar rims and threads with damp cloth. Cover with two-piece lids. Screw on tightly.