Buttercups really have a great variety of shapes and sizes, depending on where they grow.
There are also about 400 species of them!
The most familiar ones in Scandinavia are the Common buttercup & Creeping Buttercup, (Ranunculus acris L. & Ranunculus repens). Smörblomma/Smørblomst in Swedish/Norwegian, meaning "Butterflower".
The glossy/buttery surface of the flower is to attract insects.
Render in Marmoset Toolbag.