Plum Yogurt Spelt Cake with Butter Crumb Topping

As some of the Italian plums bought last week were beginning to look a little soft, I was sorely tempted to make the Crunchy-Topped Whole-Wheat Plum Cake for which Marian Burros published a recipe in the New York Times at the beginning of the month. I even purchased some Irish butter at Trader Joe's for that purpose but then I couldn't bring myself to make a cake so rich that the Man shouldn't be eating and, I knew full well, would eat nevertheless.
I still had The Bread Bible by Beth Hensperger, which I had taken out of the library last week, and as I was desultorily browsing through it, I came across a yeasted plum crumb cake that I thought would do the trick.
The recipe called for buttermilk and sour cream, neither of which I had on hand, but I did have creamy plain non-fat Greek yogurt and I decided to go for it. Naturally, half-way through, I realized that I didn't have a cake pan with a removable bottom either but by then, I was committed and I decided to go with the flow and use whatever pan we had.
Feeling all virtuous and reasonable for renouncing the buttery plum cake, I also decided it wouldn't hurt anybody's health to make the topping Beth recommends. It calls for half-a-stick of butter which equals less than 60 g (or 4 tablespoons), i.e. half-a-tablespoon per serving, and taste-wise, it really makes a huge difference. Of course some of us had many more than one serving but, hey, you only live once!

Ingredients
For the cake
400 g Italian plums, pitted (or enough to cover the surface of the pan)
162 g all-purpose flour
55 g whole spelt flour (Beth only uses all-purpose but I like to throw in some whole-grain whenever I have a chance. If I had had white whole wheat, I would have used that instead)
150 g plain non-fat yogurt (I used the Fage brand which I had bought at Trader Joe's because I like the texture. If you use another brand of plain yogurt, make sure to pick one that contains nothing but milk and live cultures)
50 g sugar
56 g vegetable oil (I used extra-light olive oil)
1 egg
zest of one lime (Beth uses lemon but we didn't have any and besides, I love the complex and exotic taste of lime zest)
pinch of salt
3 g instant yeast (Beth uses 1 tablespoon of active dry yeast)
80 g water
For the cream layer
162 g yogurt (Beth uses sour cream. I looked up yogurt as a substitute to sour cream and saw that it should be mixed with some baking soda. Of course I had no baking soda. For lack of anything better, I beat the yogurt with 5 g of corn starch but I don't think it was a valid substitution)
50 g sugar
8 g all-purpose flour
2 g vanilla extract
For the butter topping
40 g all-purpose flour
57 g cold unsalted butter, cut into pieces
50 g sugar
(Beth also uses cinnamon and mace but I like fruit desserts better without spices, except when it comes to apple pie à la mode!)


Method
Mix flours and yeastIn a large bowl combine the yogurt, sugar, oil, salt and zest, using a whisk
Add the flour progressively until it forms a smooth batter. It will be sticky and stiffGenerously butter a 9-inch quiche pan at least 2 inches deep with a removable bottom (if available). With a spatula, scrape the batter into the prepared pan. Spread with lightly floured fingers to fill pan evenlyCover with plastic wrap and let rest in a warm area until slightly puffy, about 30 minutesIn a medium bowl, combine the yogurt (adding a good pinch of baking soda, if available), sugar, flour, water and vanilla. Beat until smooth with a whisk. Set asideTo prepare the topping: in a medium bowl combine the flour and sugar (as well as spices if using). Cut the butter in until the mixture is the consistency of coarse crumbsTwenty minutes before baking, preheat the oven to 400° F/204° C. Pour the yogurt layer evenly over the batter. Gently distribute the plums over it. Sprinkle the crumb mixture to completely cover the fruitPlace the pan on the center rack of the oven and bake about 45 minutes, or until top is lightly browned and a cake tester inserted in the center comes out clean. Let the cake cook in the pan 15 minutes. Remove it to a cooling rack. Cut in wedges and serve warm or cold.The Plum Yogurt Cake goes to Susan's Wild Yeast for Yeastspotting.