Preheat the oven to 350 degrees. Grease a large baking dish.
In a large bowl, using an electric mixer, cream the butter and sugar together for 4 to 5 minutes, until light and fluffy. Continuing to mix- add the eggs one at a time. Then add the vanilla and sour cream.
In a separate bowl sift together the flour, baking powder, baking soda, cinnamon and salt. With the mixer on low, slowly add the flour mixture to the batter until fully combined.
Fold in the diced apples and finish stirring with a spatula.
To make the streusel topping, place the brown sugar, flour, cinnamon, salt, and butter into a bowl. Use your fingers to pinch ingredients together until it resembles coarse crumbs. Mix in the pecans.
Pour batter into the baking dish and spread it out evenly. Sprinkle the streusel over top. Bake for 50 minutes, or until a cake tester comes out clean. Allow to cool for 30 minutes.
Make the espresso glaze by whisking together the powdered sugar, espresso and maple syrup until smooth. Store in the refrigerator until ready to use.
Drizzle the glaze over the cake. Serve at room temperature.