Melt butter over medium heat in a large saucepan.
Add onion wedges, water mixed with MAGGI Seasoning cubes, crushed tomatoes with their juices, and 1/2 teaspoon of salt and bring to a simmer.
Cook, uncovered, for about 40 minutes. Stir occasionally and add additional salt as needed.
Blend the soup, and then season to taste.
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