Preheat oven to 300 degrees F. Butter and flour 9" cake pan. Place walnuts and 2 TBSP sugar in food processor and grind until fine. In large bowl, whisk egg yolks and sugar until blended, just a few minutes. Do not use electric mixer. Slowly whisk in walnuts and sugar mixture, then butter. Whisk in flour until mixture is homogeneous. Don't overmix.

Whisk egg yolk and water to make glaze. Pour batter in pan and paint it with egg glaze. Using the tines of a fork, mark a criss-cross pattern in top of cake. Bake 1 1/4 hours. Cool on wire rack for 10 minutes, then turn out onto cake pan.

Recipe from On Rue Tatin by Susan Loomis.