I think this is Mountain Buttercup Ranunculus montanus, photographed at the Nufenen Pass in Switzerland. This species is a plant of rocky Alpine grasslands. Like most Alpines it is low to the ground. Like many buttercups it is a remarkably shiny plant. The fly visiting one of the flowers looks like a Dolichopodidae, for those of you interested in such matters. Next to the buttercup is Lady's-mantle Alchemilla vulgaris agg.