Preheat your oven to 350° Fahrenheit. Lightly butter an 9x9 inch baking pan and set aside.
In a large mixing bowl, use a hand-held mixer to beat together the butter and granulated sugar for the cake.
Mix in the eggs, one at a time, mixing well after each addition.
Beat in the vanilla extract and sour cream just until incorporated.
In a separate bowl, whisk together the flour, baking powder, baking soda, and sea salt. Mix the flour mixture into the sugar mixture in two batches, mixing well after each addition. The batter should be fairly thick and sticky. Set aside.
For the topping, in a small mixing bowl, use a fork to mix together the all-purpose flour, brown sugar, cinnamon, and cold butter until it forms small crumbs. Stir in the chopped pecans.
Spread half of your cake batter over the bottom of your prepared pan, smoothing the top with a rubber spatula. Sprinkle half of the topping mixture evenly over the batter. Spoon the remaining cake batter in small piles evenly over the top of the topping layer and gently smooth. Sprinkle the remaining topping on top of the cake.
Bake for 30-35 minutes or until a toothpick inserted in the center of the cake comes out clean or with a few moist crumbs.
Allow the cake to cool in the pan on a wire rack for at least 20 minutes.
In another small mixing bowl, stir together the confectioner’s sugar and milk. Use less milk for a thicker glaze and more milk for a thinner glaze. Drizzle the glaze over the entire cake and serve.