Beat together the butter, sugar, eggs, vanilla paste and over-ripe banana with an electric whisk. Fold in the flour, ground almonds and bicarb of soda, then stir in the yogurt. Carefully spoon into the tin without dislodging the bananas. Bake for 45 mins-1 hr until a skewer poked in comes out with only moist crumbs. Poke all over with the skewer, about halfway into the cake, then pour over the remaining maple syrup. Let it soak in for a few mins, then carefully turn out of the tin upside-down, drizzling the banana-studded top with more syrup. Slice and serve warm.