Preheat oven to 450F. Get out your madeleine pan and set aside.

Melt some of the butter. Melt 5 1/2 tablespoons of butter in a saucepan. Set aside to cool.

Mix dry ingredients. In a medium bowl, combine the flour, baking powder, salt and lemon zest. Set aside.

Mix wet ingredients. In another medium bowl, combine the cooled butter, sugar and vanilla. Mix well. Add the eggs. Mix well and then set the bowl aside.

Melt the remaining butter. In the same saucepan you used to melt the butter, melt an additional 1 tablespoon of butter. Set aside.

Combine wet and dry ingredients. Add the dry ingredients to the wet ingredients. Mix well until there are no dry bits of batter visible.

Grease the pan. With a pastry brush or using a spoon and your finger tips, grease the madeleine pan with the remaining 1 tablespoon of butter. Make sure each well is thoroughly greased but that the butter does not pool at the bottom of the well.

Assemble the tea cakes. Into each madeleine well, spoon about 1/2 tablespoon of batter. In the center of the batter spoon about 1/2 teaspoon of blueberry jam. Top with another 1/2 tablespoon of batter.

Bake. Place the tin in the oven and bake for 4 minutes.

Lower the temperature. Reduce the oven temperature to 350F and bake for another 4 minutes. The cakes are done when they are golden and spring back when you touch one gently with a fingertip.

Cool. Allow the cakes to cool for 5 minutes, then remove from the pan and let them cool a bit more on a wire rack.

Serve. Dust the cakes with confectioners sugar and serve.