Prepare the vegetables: Cut onion into thin slices. Remove the husk and silk from the corn, then stand it up vertically and carefully run a chopping knife down to cut/scrape the kernels off (it might help to cut it in half first if you can).

Put butter in a heavy pot and melt over medium heat. Once melted, add the onions and cook while stirring until starting to turn golden brown and soft (about 10-15 minutes).

Add about 1/2 tsp salt and the corn kernels. Cook an additional 2-3 minutes, stirring.

Add the water and bring to a boil. Turn to low heat and simmer for 5 minutes.

Stop the heat and puree the soup until smooth using a hand mixer, food processor or blender. If you don't like the grainy texture, strain the soup through a fine-ish sieve.

Adjust the the taste with more salt. Serve into bowls and sprinkle with pepper if desired.