Over medium high heat warm up the oil in a large pot. Add the onions and cook for 3-5 minutes, until soft and lightly browned. Add garlic, cook until fragrant, then the potatoes and stir for 30 seconds. Next add all vegetable stock, stir and cover the pot.
Bring to a boil, then let simmering (lower the heat if necessary) for 20 minutes, stirring occasionally.
Rinse sauerkraut under cold water, until some of the sour taste is gone. Add to the potatoes along with chopped tomatoes and stir until incorporated.
Whisk in the rest of ingredients. With a spatula or fork pull the sauerkraut over the potatoes, so those are hidden underneath. Cover pot with lid and cook like this for another 25-30 minutes, stirring occasionally, until potatoes are fully cooked and sauerkraut is tender.
Remove from heat, taste to see if it needs more salt. Serve warm.