In the male of the Meadow Brown (Maniola jurtina), the top of the forewings is brown with an black "eye spot" in the tip of the forewings (2nd & 4th photo).  
The female has an orange field on the forewings, and the black eye spot usually has a white core (1st, 3rd & 5th photo). 
Sometimes there is a double white core in the spot in the wing tip.
Confusion with the Gatekeeper (Pyronia tithonus) is possible, but the Meadow Brown has no orange on the hindwing, or very little (5th photo), while in the Gatekeeper the hindwing is orange with a wide brown edge.

Paul de Arzila Nature Reserve, Coimbra, Portugal, 10 & 11 June 2023