In a bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, add eggs, sugar, butter, and vanilla. Beat until it begins to come together. It is okay if it looks curdled, it comes together. Add the dry ingredients. Mix until just moist. Add sour cream. Mix until smooth. In a bowl, mix together walnuts, both sugars, cinnamon, and vanilla.

Spray the pan with baking spray. Spoon half of the batter into the bottom of the pan, spread around. Sprinkle with streusel. Add another layer of batter and another layer of streusel.

Bake in a preheated 325 degree oven for 40 to 50 minutes. Cool completely.