perhaps Red Trillium, Wake-Robin (Trillium erectum), yellow form? or perhaps yellow center T. flexipes?

Hawk Mtn., PA (May 13, 2006)

see below for further study:
"some populations have white, yellow-green, or paler red flowers"
https://gobotany.newenglandwild.org/species/trillium/erectum/

http://www.discoverlife.org/mp/20p?see=I_CAM69292&res=640
https://florapittsburghensis.wordpress.com/2015/05/05/wake-robin-trillium-erectum-yellow-form/
https://plants.usda.gov/core/profile?symbol=TRER3
https://plants.usda.gov/core/profile?symbol=TRER