I might like a good superlative as much as the next person, but I'm not one to throw around words like "amazing" and "the best" lightly when it comes to a recipe. In fact, I probably wouldn't use them myself to describe this particular coffee cake. I will say, however, that the lucky people who got to eat this cake used those exact words to describe this moist, tender, light and crazily addictive cake.
Backtracking for a moment, the reason that I wanted to make this cake in the first place was twofold: I had a mostly-unused container of sour cream sitting around in my fridge that was looking for a recipe to work itself into and I had a package of Nutorious nuts that were also looking for a job.
Nutorious is a Wisconsin company that makes gourmet candied nuts. I'm not necessarily a big nut fan, but theirs are really outstanding. They use a mix of nuts and they come in flavors like Cherry Vanilla and Cranberry Orange. It is easy to breeze through one of their bags in no time flat, especially if you have someone to help you much, but the company goes out of their way to point out how good the nuts are in various recipes, so I wanted to try them out in something. I ended up using a mixture of their Original and Cherry Vanilla flavors with excellent results, as the candy coating blended right into the cake. Any candied or sweetly spiced nut will work in this recipe, and you can always opt for plain, toasted nuts, too. Nutorious mixes walnuts, pecans and almonds, so try to use a blend if you're not using theirs.

Sour Cream Streusel Coffee Cake
Streusel
1/2 cup all-purpose flour
1/3 cup sugar
1/3 cup chopped candied/toasted nuts (Nutorious or other)
1/4 cup butter, melted
1/4 teaspoon vanilla
1/4 tsp salt

Cake
1 cup sugar
1/2 cup butter, softened
1 teaspoon vanilla
2 large eggs
2 cups all-purpose flour
1 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup sour cream (light is fine)
1/3 cup chopped candied/toasted nuts (Nutorious or other)

Prehat oven to 350F and lightly grease a 9-in square pan.
In a medium bowl, stir together all topping ingredients until wet crumbs are formed. Set aside.

In a large bowl, cream together sugar and butter until light. Beat in vanilla, followed by the eggs, adding them one at a time until mixure is smooth.
In a medium bowl, whisk together flour, baking powder, baking soda and salt. Add to sugar mixture, alternating with sour cream in two or three additions, until well mixed. Stir in nuts and scrape into prepared pan. Top with streusel mixture, spreading it into as even a layer as possible.
Bake for 35-45 minutes or until toothpick inserted into the center comes out clean.
Cool on a wire rack for at least 30 minutes before slicing.
Serves 12.