Step 1Place the sugar and the vanilla bean seeds in a medium, heavy-bottomed saucepan. Add enough water to moisten all of the sugar. Be sure to brush down the sides of the pot with a pastry brush to remove any stray sugar granules. Cook the sugar over high heat until it caramelizes and turns golden, about 4 to 5 minutes. Add the rhubarb and the wine. Cook, stirring, over high heat, until the rhubarb softens and becomes a pulp. (Be careful; the mixture will splatter.)
Step 2Add 1/3 of the strawberries to the pot and stir quickly into the rhubarb pulp, working over high heat. Cook until the berries turn into jam and the liquid has mostly evaporated from the pot, about 8 minutes. Add another 1/3 of the berries and quickly stir until just softened. Add the last batch of berries, turn off the heat, and stir gently. Allow the jam to sit undisturbed about 10 minutes. If using to fill the doughnuts, refrigerate the jam so it sets up and filling is easier. Keep refrigerated.