Preheat the oven to 325F and grease a 9-inch round springform cake pan.

With your fingers, pinch together the butter with the flour, sugar, cinnamon, and salt in a bowl until a crumbly, sandy texture forms. Add the almonds and stir to incorporate. Set aside. 

Sift the flour, baking powder, and salt into a bowl. Set aside. 

Using a stand mixer fitted with a paddle attachment, cream together the butter and sugar on medium speed until it becomes fluffy, about 1-2 minutes. Add the egg, milk, and vanilla and mix until combined, about 1 minute. Add the sifted flour and baking powder into the wet ingredients and beat until the batter is just combined. Pour the batter into the cake pan and sprinkle the streusel evenly on top. Transfer into the oven and bake until a cake tester comes out clean, about 50 minutes.

Let the cake cool. Loosen the edges of the cake from the pan with an offset spatula, unmold the cake and serve.