Method

1. To make the crumbs:

Put all of the ingredients except the butter and vanilla in the bowl of a stand mixer fitted with the paddle attachment (see headnote for other options) and mix on low just to combine. Add the pieces of cold butter, toss them around until they’re coated and then beat on medium-low until the ingredients form moist clumps. Squeeze some, and the crumbs should hold together. Getting to this stage can take a few minutes, so don’t rush it. Add the vanilla and mix until incorporated.

Remove the bowl from the mixer stand, reach in and grab a spoonful or two of the mixture at a time between your fingers and squeeze, so that you get little balls of crumbs. Cover (in the bowl or in another container) and chill until needed. If you can give the crumbs at least an hour, that would be great; 2 to 3 hours or more (or 30 minutes or more in the freezer) would be ideal. (You can make the crumbs up to 3 days ahead; keep tightly wrapped in the refrigerator.)

2. To make the cake:

Center a rack in the oven and preheat it to 350 degrees F. Butter a 9-inch square baking pan, or use bakers’ spray. 

Whisk the flour, baking powder and baking soda together.

Working in a large bowl, whisk the sugar and salt together. Add the ricotta and whisk to blend well. One by one, add the eggs, whisk until each is incorporated. Whisk in the melted butter. When the mixture is blended, switch to a flexible spatula and gently fold and stir in the dry ingredients until you’ve got a heavy, smooth batter. Scrape the batter into the pan, spreading it evenly and taking care to nudge some into the corners. Scatter the fruit over the batter.

Remove the crumbs from the refrigerator (or freezer) and top the cake with them, grabbing a little of the mixture each time and squeezing it so that you end up with a really bumpy layer.

Bake the cake for about 50 minutes, or until the top is golden brown, whatever fruit you can see is bubbling up through the crumbs and, most important, a tester inserted into the center of the cake comes out clean. Transfer the pan to a rack and let rest for 3 minutes, then run a table knife between the cake and the sides of the pan. Let the cake settle for about 10 minutes and then unmold it onto the rack; invert and cool right side up. The cake is ready to enjoy when it is only just warm or after it has reached room temperature.

I usually cut the cake into 16 squares, but cut for your crowd.

3. Storing:

Wrapped well, the cake will keep for up to 4 days at room temperature or for up to 2 months in the freezer; defrost, still wrapped, at room temperature.