From Cook’s Illustrated’s The Best Recipe
2 c (10.5 oz) flour
1 c plus 2 tbs (9.5 oz) sugar
1 tsp salt
10 tbs butter
1 tsp baking powder
½ tsp baking soda
¾ c buttermilk of low-fat (not nonfat) plain yogurt
1 egg
1 tsp vanilla
1 c (3 oz) walnuts or pecans
½ c brown sugar
1 tsp cinnamon
Preheat oven to 350F, spray a 8 or 9” springform pan with pam w/ flour.
Combine flour, sugar, and salt in food processor, pulse to combine. Add butter, pulse until mixture resembles coarse crumbs. Remove all but 1 c to bowl of stand mixer fitted with whisk. Add baking powder and soda to mixer bowl, stir to combine. Add buttermilk or yogurt, egg, and vanilla, beat until batter is thick, smooth, fluffy, and frostinglike, 1 ½ to 2 minutes.
Add nuts to mixture in food processor, pulse several times to chop. Add brown sugar and cinnamon to food processor, pulse to combine. Scrape half of the batter into the pan, top with half of the crumb mixture, then remaining batter, and remaining crumb.
Bake until center is firm and toothpick comes out clean, 50 to 55 minutes.