We present a new structural study of a D₂–M₂ tectono-thermal structure in SW Iberia (Ponte de Sor–Seda gneiss dome) characterized by a spatial distribution of telescoping isograds providing a record of Buchan-type metamorphic conditions. The gneiss dome comprises an infrastructure made up of a lower gneiss unit (LGU) and an intermediate schist unit (ISU), separated by early D₂ ductile extensional shear zones. The LGU and the ISU are composed of Ediacaran–Cambrian rocks that experienced the highest-grade M₂ metamorphic conditions (amphibolite facies). Late Ediacaran–Early Terreneuvian and Late Miaolingian–Early Furongian protolith ages for LGU (496 ± 3 Ma) and ISU (539 ± 2 Ma) orthogneisses are reported. A superstructure made of Cambrian–Devonian rocks (Upper Slate Unit, USU) deformed under M₂ greenschist facies conditions, tectonically overlies the ISU across a D₂ extensional shear zone. Kinematic criteria associated with D₂–M₂ fabrics indicate top-to-ESE–SE sense of shear. A late-D₂ brittle-ductile high-angle extensional shear zone (Seda shear zone) crosscuts the gneiss dome. D₃ upright folds, thrusts and transpressive shear zones caused the steepening of D₂ structures and the local crenulation of S₂ foliation. The Mississippian D₂–M₂ event recorded in the Ossa–Morena Zone may be regarded as a regional-scale phenomenon that markedly influenced the crustal architecture of North Gondwana during the assembly of Pangaea.