Combine rhubarb, strawberries, and sugar in a large glass bowl. Stir thoroughly to combine. Cover with plastic wrap and refrigerate for at least 12 hours, up to 24.

When ready to can, take your fruit out of the refrigerator. Add seeds of the vanilla bean. Prepare your jars by washing them with soapy water. Add them to your water bath canner with the wire rack, and bring to a simmer.

To make jam, add rhubarb mixture to a large heavy-bottomed pot. Add the lemon juice and salt. Bring to a boil over medium-high heat, stirring occasionally.

Once the mixture starts boiling, it will begin to foam. Stir every few minutes as the jam continues to cook down and thicken.

Towards the 22 to 25 minute mark, the jam will begin thickening. Stir often and watch your heat.

When jam is thickened, take each warm jar out of the water and set it on a kitchen towel. Fill with hot jam, leaving 1/4 inch headspace. Screw the lids on until finger tight.

Return the filled jars to the canner and bring the water to a boil with the lid on. Process for 10 minutes.

Let fully cool on a kitchen towel on the counter, and let them seal. Store in a cool, dark place for 1 year.