Rowan Berry Marmalade (dvs rönnbär!)
1 litre of rowan berries
2 grapefruits (I used blood grape)
2 lemons
10 dl of water (though I used about 5-6 in the end I think)
14 dl of sugar (I used 13 dl of white sugar and 1 dl of brown ecological sugar, this was because we were all out of sugar, all stores were closed because it was Sunday. Bought a package at the candy store next to me for 26 kr in desperation. Otherwise my plan was to use way more natural brown sugar instead of the refined.)

Found the recipe here!

Pick rowan berries, rinse them in water and put in the freezer for some hours to a day. This is supposedly making them less sour.
Then take the berries, peel the the grapes and the lemon, cut what’s left in to pieces and put it in with the berries. Boil on low heat for about 45 minutes. Put the sugar in and boil hard for another 15-20 minutes. Remove the foam, put in jars, done!
I think it was great! I love that it’s not as sugary tasting as regular marmalade that I haven’t really ever been very fond of. Still, it does contain a lot of refined sugar but no chemicals which I always consider a big plus!

Some other things I learned with a quick search on the internet that you can do with rowan berries: dry them and put in bread, dry them or freeze and eat a couple a day to get vitamin c, make a juice to drink with your food, and plenty of forms of ancient magic.
A lot of people on forums and stuff also claim that they have not had as many colds since they have started eating 1-4 dried berries/day