1) To prepare the topping: Whisk together the flour, sugar, cinnamon, and salt.
2) Crumble in the almond paste, and add the almond extract.
3) Work in the cold butter till the mixture becomes crumbly. Set aside.
4) Preheat the oven to 350°F. Grease and flour a 10" x 10" or 9" x 13" pan.
5) To prepare the cake: Beat together the butter, sugar, salt, baking powder, and extract until fluffy.
6) Add the eggs one at a time, beating well after each.
7) Add the flour in thirds, alternately with the sour cream, blending well after each addition.
8) Spread the batter in the prepared pan.
9) Top with the cherries and streusel topping.
10) Bake the cake for 55 to 65 minutes, until a toothpick inserted near the center comes out clean. Remove from the oven.
11) While the cake is baking, prepare the glaze. Combine the confectioners' sugar, almond, and just enough of the milk to make a pourable glaze.
12) Drizzle it over the still-hot coffeecake.
13) Garnish with toasted sliced almonds, if desired. Serve warm or at room temperature.