Take the spices you like! I used Swedish curry (contains coriander, cayenne, fennel, turmeric and cumin among other spices), extra cumin, chili flakes and thyme.
Chop the onions (I forgot the garlic so I added it later)
Fry the onions and the garlic in butter and some paprika (dried)
and the chopped fresh tomatoes.
Also add the spices. I used some frozen herbs since I didn't have fresh at home. Let it boil for approx. 10 minutes. Note that the salt shouldn't be added while the soup is boiling.
When the soup is ready add a pinch of salt and perhaps some vinegar to sharpen the flavor. This is a very easy yet tasteful dish that works really well when it's getting colder outside.
I realized that I forgot to add the water to the supplies tab the last time I published this guide so here we go again!