Preheat oven to 325°F (160°C).

Grease a 13x9 inch pan.

In a large bowl, cream together the butter and sugar until light and fluffy using an electric mixer.

Beat in the eggs one at a time, then stir in the vanilla.

In a separate bowl, whisk together the flour and baking powder.

Gradually add the dry ingredients to the wet ingredients, alternating with the milk, mixing until just combined.

Pour the batter into the prepared pan.

In a large casserole, combine the maple syrup, brown sugar, cream, and butter.

Bring the mixture to a boil over medium heat, stirring constantly.

Reduce heat and simmer gently for 2 minutes, or until the sauce has slightly reduced.

Carefully pour the hot maple syrup sauce over the cake batter in the pan.

Bake for 35 minutes, or until the cake is light brown and a toothpick inserted into the center comes out clean.