Tough cake

Be careful not to overmix when adding the milk/flour to the batter in an American-stye creamed butter+sugar cake. Combine until no flour streaks remain and ingredients are combined, but not further.

Oil-based cakes tend to be more delicate and tender, as do those where the eggs are separated, the yolks are beaten with sugar to "form the ribbon" and the beaten whites are folded in.

Another method is to mix the dry ingredients, add the softened butter until a dough-like consistency is reached, then beat in the liquids. (Just used this method for the first time, but we won't try it until tomorrow, though the batter itself had a beautiful airy texture, so it seems promising).

Have you checked your oven temperature accuracy with an oven thermometer?