Step 1

Combine the raspberries, sliced plums, sugar, lemon juice, and orange zest in a large heavy-bottomed pot. Place over medium high heat and stir frequently as the sugar dissolves and the fruit begins to release its juices.

Step 2

Continue to cook, stirring frequently as the jam simmers and thickens. Skim any foam off of the surface with a spoon.

Step 3

(Optional) While the jam is simmering, remove plum skins with a spoon. It is slightly tedious but I prefer the texture of the jam without the skins.

Step 4

(Optional) If you prefer fewer raspberry seeds, simply place a mesh strainer over the pot. Ladle ⅓-½ of the mixture into the strainer and push it through with a spatula back into the pot. Discard raspberry seeds.

Step 5

Once the jam is reduced and thickened (see tip above), remove from heat and ladle jam into sterilized jars. Top with a lid and screw on with a ring.

Step 6

Process jars in a water bath for 10 minutes (15 minutes for 5,000+ ft elevation). Remove from water bath and let cool. Check that lids have sealed by pressing down into the center of each one. It should not move.

Step 7

Store jam in a cool dry place like a pantry and consume within 1 year.