A rich, moist Coffee Cake with a perfect crumb and that just right crunch. Perfect with coffee or an after-dinner treat
Process the pecans and sugar in the food processor till they are finely ground (You can also chop the nuts finely and mix with the brown sugar). Add flour, cinnamon, and salt. Pulse or mix to combine. Add melted butter, water and combine again. The streusel should be crumbly and slightly moist. Transfer to a bowl and set aside.
Preheat the oven to 350º F. Adjust the oven rack to the lower-middle position.
Grease and flour a 9 inch round springform cake pan and line the bottom with parchment paper. I do this extra step for butter cakes to avoid getting the cake stuck to the bottom. Place on a rimmed baking sheet.
Combine the flour, sugar, salt, cinnamon, baking powder and baking soda. Add butter.
Food Processor - Pulse until very small pieces but visible pieces of the butter remain in the flour mixture, about 5 seconds. Add milk, egg, egg yolk and vanilla until the dry ingredients are moistened. Scrape down the sides and pulse to combine. Transfer to the cake pan and smooth with a rubber spatula.
Kitchen Mixer - Use the paddle attachment and stir at medium speed till very small pieces but visible pieces of the butter remain in the flour mixture. Beat the egg and egg yolk together just to combine and add to the flour and butter mixture. Add milk and vanilla and stir to combine. Transfer to the cake pan and smooth with a rubber spatula.
The batter will be thick. Be sure to use a silicone spatula to scrape all the batter into the cake pan.
Starting at the edges of the pan, sprinkle streusel in an even layer over the batter.
Bake for 40-55 minutes. Check at 40 minutes first by shaking the cake pan gently to see if the batter is still jiggly. If it is, then bake for 10 minutes more. DO NOT insert a toothpick to check. If the cake is firm, then check with the toothpick/skewer inserted into the center of the cake. The toothpick should come away clean. The cake is done.
Cool completely for 2 hours. DO NOT SKIP THIS STEP. The cake is still cooking even though it is out of the oven and needs the cooling time to bind the ingredients together.
After it is completely cool, release the cake from the springform. Place a plate inverted over the cake and flip it in one quick motion. Remove the parchment paper. Place the serving platter inverted over the cake (the bottom side is up now) and flip it back quickly, right side up.
Dust with powdered sugar. Using a serrated knife, cut the cake into wedges and serve.