• Preheat your oven to 350°F (or 177°C) and grease a springform pan (9'' or 10'')

Cake

• Use a hand or electric mixer to whip the butter with ¾ cup of sugar until creamy (2 minutes at high speed). Add the large eggs one at a time at medium speed, mixing thoroughly after each, then toss in the sour cream and vanilla extract.
• Mix in the baking soda, baking powder, flour, and salt until smooth (2-3 minutes at low speed). Gently fold in the juicy blackberries. Spread the creamy batter into your greased pan and set it aside.

Cream Cheese Topping

• In a clean bowl, beat the full-fat cream cheese with the remaining sugar (about ¼ cup) until smooth. Spoon the mixture over your cake batter.

Crumb Topping

• Mix the flour, cinnamon, and brown sugar in another bowl. Cut the cubed butter into the mixture until it looks like little pea-size crumbs, then sprinkle it evenly over the cream cheese topping.

Baking

• Bake for 60 to 65 minutes until the center doesn't jiggle much. The small toothpick poked into it should be clean when pulled out with just a few crumbs. After about 30 minutes, cover the cake loosely with foil to keep its edges from getting too brown.
• Let it cool in the pan for 30-40 minutes. Then, carefully remove the pan's sides to release the cake.

Icing

• Whisk together our icing ingredients until smooth. Add a splash of lemon juice, cream, or milk if you want a bit runnier. Drizzle over the still-warm cake. Enjoy your blackberry cheesecake!