For maximum streusel effect, just flip the script, and the cake.
With all due respect, when it comes to coffee cake, nobody’s in it for the actual cake—it’s all about the crumbly, buttery cinnamon streusel on top. So why not maximize the streusel-to-cake ratio? I’m talking equal parts crumb and cake.
Deb Perelman of Smitten Kitchen learned a smart hack from Gina’s Pastry Shop in New Jersey, the bakery she worked at in high school, that allows you to double or even triple the usual amount of streusel topping. All it takes is thinking in reverse. Crumble the mixture of brown sugar, butter, and cinnamon at the bottom of a pan, spread the cake batter over it, bake, and then flip the whole thing over—revealing a perfectly smooth, golden crown of cinnamony streusel.
I like to put the technique to work in a cast-iron skillet that’s deep enough to accommodate a near absurd amount of streusel and a healthy portion of batter. The skillet transfers and holds precisely the right amount of heat for an evenly baked cake with crispy edges. (A glass baking dish retains too much heat, leading to burnt bottoms and undercooked centers.)
As for the cake batter, it’s a light and fluffy undercoat to the dense crumb layer, thanks to yogurt and mayonnaise (trust me here). Yogurt adds tang, while mayo brings moisture without being too rich or oily—or announcing its eggy, vinegary presence at all. Together, they make a cake that stands up to a full inch and a half of cinnamon streusel but never competes with it.