Preheat oven to 350 ° F. with rack in centre of oven. Grease an 8 or 9-inch springform pan and line the bottom with a circle of parchment paper.
In a large bowl with a hand mixer of the bowl of your stand mixer with the paddle attachment, cream the butter until light and fluffy. Add the sugar and beat until light and fluffy. Add the eggs, one at a time, beating well after each addition. Add the vanilla and yogurt and mix to combine.
In a medium bowl, whisk together the flour, baking powder, baking soda and salt. it. Add to bowl with batter and mix to combine.
Add batter to prepared pan and level. Sprinkle blackberries evenly over the top of the batter. Place springform pan on a baking sheet and bake in to the pre-heated oven for 30 minutes. Gently remove cake from oven and sprinkle sliced almonds evenly over the top. Sprinkle with sugar. Return to the oven and continue baking an additional 25-30 minutes, or until a cake tester comes out clean. (*If cake or almonds are darkening too quickly, cover the top loosely with a piece of aluminum foil for the last part of baking.
Allow to cool in pan for 10-15 minutes, then run a knife around the outside of the cake and remove the outer ring. Allow to cool completely before removing cake from bottom of springform pan.
Serve garnished with powdered sugar. Also nice served with a dollop of whipped cream, creme fraiche or ice cream.