I baked a nice chocolate cake for cake pops, used an equal part butter flour sugar recipe. Baked it in a fan oven 160c in a single 7" tin left it till it was springy, and skewer came out clean. Left it in the tray for 5-10mins then placed on wire rack. But after it cooled and I mashed it, it seemed quite oil and I don't know why. Maybe it could of been baked a little longer.
When I mixed with the buttercream they look quite oily and shiny.

Any ideas?

Ps I am using gluten free flour. Not sure if this will have any affect.