Adonis vernalis, also known as pheasant's eye. It's considered as a common spring flower in some well-preserved (means conservation areas, where only limited human presence allowed) parts of the country, but what's not so well known, that it's rather poisonous due to some cardiostimulant compounds. A strong tea out of it would be fatal. 

Her relative, the Adonis transsylvanica is, however a very rare plant;  rare enough to be the primary reason to establishing a National Park on it's conservation. There's only five known habitat exists in the Carpathian Basin, and as for today, worldwide.