1 heaping cup (125g) fresh or frozen blackberries (do not thaw)
one 8-ounce block cream cheese, softened to room temperature
1/3 cup (67g) packed dark or light brown sugar
1/2 (62g) cup all-purpose flour
1 and 1/2 teaspoons ground cinnamon
3 Tablespoons (43g) unsalted butter, cold and cubed
Preheat oven to 350°F (177°C). Grease and lightly flour a 9 or 10-inch springform pan.
Make the cake: Using a handheld or stand mixer fitted with a paddle attachment, beat the butter and 3/4 cup granulated sugar together on high speed until creamy and combined, about 2 minutes. On medium-high speed, add 1 egg at a time, beating well after each addition. Beat in the vanilla extract and sour cream. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. Add the flour, baking powder, baking soda, and salt. Turn the mixer on low speed and beat until completely combined. Using a rubber spatula or wooden spoon, fold in the blackberries.
Spread the batter into the prepared pan. Set aside.
Using a handheld or stand mixer fitted with a paddle attachment, beat the cream cheese and remaining 1/4 cup granulated sugar together until combined. Spoon and spread over cake batter. It's a thick cream cheese topping, so do your best to spread around. Set aside.
Make the crumb topping: Combine the brown sugar, flour, and cinnamon together in a medium bowl. Cut in the chilled butter with a pastry blender or two forks (or even with your hands) until the mixture resembles pea sized crumbs. Sprinkle evenly over cream cheese layer.
Bake the cake for 60-65 minutes or until it no longer jiggles in the center. A toothpick inserted in the center should come out *mostly* clean. A few moist crumbs are ok. I like to loosely cover the top of the cake with aluminum foil at the 30 minute mark to prevent over-browning.
Allow the cake to cool completely before slicing and serving. I like to place it in the refrigerator after 30 minutes of cooling at room temperature. This speeds things up.
Slice and serve. Store leftovers in the refrigerator.
We used a pint of fresh blueberries, which was good.
It took at least 15 minutes longer in the oven than the directions said.
A toothpick wasn't a great indication of doneness. Bake it until the center no longer jiggles.
We ate it cold (refrigerated) the next day and that was really good.