Combine topping ingredients in a food processor or mix well until small crumbs are formed. Transfer to a plate and refrigerate until firm, about 10 minutes.
In a small saucepan, melt butter over medium-low heat and cook until the butter is brown, about 5 minutes, then pour into a bowl and freeze until firm but not completely frozen, about 10 minutes.
Preheat oven to 350 degrees F.
Mix together firm browned butter, sugar, and eggs in a large mixing bowl. Fold in sour cream and vanilla and mix well. Add in flour, baking powder, and salt, and mix until everything is combined.
Scrape cake batter into a cake pan and top with chilled topping. Bake for 45 minutes or until the middle is cooked through.
Top with powdered sugar and cinnamon before serving.
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