Gateau Breton

1. Take a bowl, and add sugar, buckwheat flour, and baking powder together. Blend well.
2. Pull out egg yolks from the eggs and put aside one of them to flavor the cake with before baking.
3. Build a well in the middle of the flour/sugar mixture. Include egg yolks and mix thoroughly using a wooden spoon. Next, knead the dough with fingers until crumbly. 
4. Cut and add the butter into the dough until evenly spread.
5. Grease a spring-form baking pan/tin with butter and spread the dough into it. Brush the top of the cake with the egg yolk set apart earlier and then, slit through the top of the cake with a fork several times in each direction to create a diamond/rhombus pattern.
6. Bake in the oven (180 degrees C or 360 degrees F) for nearly 45 minutes.
7. Let the cake stand and cool in the pan/tin for about ten minutes before serving.

Trivia

It is thought that Gateau Breton used to be baked by the spouses of laborers and anglers as a delightful treat for their husbands when returning home from hard days and evenings of work in the fields or adrift.

It's served in little cuboids or rhomb-formed (diamond-shaped) chomps. The combo of this cake and a glass of milk or a cup of coffee is loved by many.