For crumb topping: in a large bowl, mix together flour, brown sugar, cinnamon, vanilla, and salt with a fork. Add melted butter and use fork to mix butter into the mixture until just combined into a chunky, crumbly topping. Set aside.
For cake: in the bowl of a mixer, cream together butter and sugar for about 90 seconds on medium speed until light and fluffy.
Add sour cream, eggs, and vanilla. Mix on low until combined, scraping down side of bowl as needed.
In a separate bowl, whisk together flour, baking powder, baking soda, and salt until combined.
Add flour mixture to wet ingredients in mixer. Combine on low speed until just incorporated. Don’t over-mix! Batter will be sticky.
Scoop batter into prepared pan, spreading out in an even layer.
Add crumb topping in an even layer to top of batter. Don’t press crumb into batter (let it rest on top).
Bake at 350℉ for 40-50 minutes, until crumb is set and a toothpick inserted in center of the cake comes out with few moist crumbs.
Let cool in the pan on a wire rack for at least 20 minutes before slicing and digging in!
Video
Notes
Bring eggs and sour cream to room temperature about 30 minutes prior to baking for best results!