In a pot with tightly fitting lid melt butter and saute chopped onion until translucent.
Add 4 cups water and bring to a boil.
Stir in 1 cup buckwheat grits or groats.
Reduce heat to very low, close the lid of the pot and let simmer for about 30 minutes until buckwheat reaches polenta consistency. I found that sometimes (maybe depending on whether you use grits or groats or coarsely ground buckwheat) it already thickens after about 10 minutes, so have a look at it after 10 minutes.