Beat the egg with the brown sugar until quite frothy.
Beat in the butter, oil and vanilla and work until the sugar is mostly dissolved.
Sift the dry ingredients together and use a whisk to stir them into the wet ingredients gently by hand until just mixed.
Lightly oil a 7 x 11 pan and spread the batter out evenly.
Bake in a preheated oven 350 Degrees F oven for 35 minutes (until a skewer comes out dry or with a little crumb).
Let cool completely before cutting.
Sift a little powdered sugar on the top after cutting but before serving.