Prepare a canning pot and four half pint jars.

Wash the berries. Remove hulls and dice them.

Place the chopped strawberries in a large bowl. Add the sugar, pectin, and vanilla bean seeds. Stir to combine and let the strawberries and sugar sit until the berries begin to release their juice and the sugar is mostly dissolved. With ripe berries, this should only take a minute or two.

Pour strawberries and all the syrup into a low, wide pan. A 7 or 8 quart Dutch oven is a good choice. Add the lemon zest and juice and stir to combine.

Bring the fruit to a boil over high heat. Once it is bubbling, reduce the heat to medium-high, to ensure that it doesn’t boil over. Cook, stirring regularly, until the fruit has reduced by approximately half. When it is done, it will look thick and the color will have darkened.

If you’re uncertain about whether it is done, you can test for set by stirring your spatula through the cooking jam and then holding it up over the pan. If it is done, the droplets hanging off the spatula will be thick and viscous, like corn syrup or honey that has been stored in a cool place.

Once jam has thickened sufficiently, remove the pan from the heat. Funnel the jam into your prepared jars. Wipe the rims, apply the lids and rings, and process in your canner for 10 minutes.

When time is up, remove jars from canner and let them cool on a towel-lined counter top. When jars are cool enough to handle, remove rings and check seals. If any jars are not sealed, store them in the fridge and use them first. Store sealed jars in a cool, dark place for up to one year.