Harvest fresh grape leaves while they're still tender, through early summer. This recipe makes just 2 pints, so if you have lots of grape leaves, double or triple the recipe.
Add enough water to the grape leaves to cover. Stir in 2 Tbsp. of the lemon juice. Weight leaves down with a plate. Let stand 20 minutes. Drain.
Meanwhile, bring a large pot of water to boiling. Add grape leaves to boiling water. Cover and return to boiling, then boil, uncovered,1 minute. Transfer leaves to a large bowl of ice water. Stir until chilled, about 2 minutes, then drain well.
Stack 6 leaves, rough bottom sides up. Roll up from the stem end and arrange vertically in 2 pint jars. Repeat with remaining leaves.
For brine, bring 3 cups water to a boil. Add 2 Tbsp. red wine vinegar, the remaining 2 Tbsp. lemon juice, and the salt, stirring to dissolve salt.
Add brine to jars leaving about ½ inch headspace. Remove air bubbles from jars by pressing the leaves gently with a wooden spoon. Add more brine as needed to maintain ½ inch headspace. Seal jars. Let cool completely, then store in the refrigerator up to 6 months.