Prepare a boiling water bath canner and enough jars to hold two pints.

Combine the berries and sugar in a low, wide non-reactive pot. Stir to combine and let it sit until the sugar begins to dissolve.

Put the pot on the stove over high heat. Bring the jam to a boil and reduce the heat to medium-high. Cook, stirring regularly, for 12-20 minutes.

Towards the end of cooking, add the lemon zest and juice.

Check for set using your favorite method.

When you've deemed that the jam is thick enough, remove the pot from the heat.

Funnel the finished jam into the prepared jars, leaving 1/2 inch headspace.

Wipe the rims, apply the lids and rings, and process in a boiling water bath canner for 10 minutes.

When the time is up, remove the jars and set them on a folded kitchen towel to cool. When the jars have cooled enough that you can comfortably handle them, check the seals. Sealed jars can be stored at room temperature for up to a year. Any unsealed jars should be refrigerated and used promptly.