Fill a canning pot with water and start heating to a boil. Separate jar lids, screw bands, and jars.
Measure exact amount of sugar into a large bowl and set aside.
Wash and hull strawberries, then in a large bowl crush one layer at a time using a potato masher, leaving some chunks. Pour berries, juice and all, into a 6-quart dutch oven or nonreactive stockpot and add lemon juice.
At this point, put the empty jars into the pot of water to heat and sterilize.
Begin heating berries over medium-high heat, then stir in pectin. Continue heating until it reaches a rapid boil, then add sugar all at once, stirring to dissolve.
Split the vanilla beans and scrap out as much caviar as possible into pot, then toss entire bean in too.
Continue heating and stirring until sugar is completely dissolved. Cook until mixture is thickened and jammy. Test for doneness by spooning some jam onto a chilled plate and letting cool. Touch to see if a skin is forming and feels gel-like; if so, jam is ready. Remove from heat.
Using tongs, remove jars from pot and place on a towel-covered countertop.
Carefully pour jam into jars, leaving about 1/2 inch headspace. Wipe edges clean and place lids on top, securing with screw bands. Gently lower jars into hot-water bath and process (let boil) for 10 minutes.
Remove and set on toweled counter. Let rest for 24-48 hours before moving. At some point you should hear the jars "ping" — this means the seal was properly made and it's safe to leave in your cupboard. If a jar doesn't ping, you can either re-process or store the jar in the fridge.
Notes
If using low-sugar pectin, please follow the box directions for ingredients and sugar levels.