Preheat Oven to 350°F. Butter and flour two 8 inch cake pans and line with parchment.
To make cake: In a small bowl, whisk eggs and sour cream together. Set aside.
In the bowl of an electric mixer fitted with a paddle attachment, cream the butter, baking powder and salt on low speed until softened, about 2 to 3 minutes, Add the sugar and increase speed to medium for 3 to 4 minutes until batter is light and fluffy, scraping down the sides of the bowl as needed. Reduce speed to low and in three additions alternate adding the dry ingredients and wet ingredients, mixing until just combined.
Transfer batter to prepared baking pans. Spread the mixture evenly in both pans.
For cream cheese filling: In the bowl of the electric mixer fitted with a paddle attachment, beat the cream cheese on medium speed until light and fluffy, about 5 minutes, scraping down the sides of the bowl frequently. Add the eggs, one at a time, making sure each egg is fully incorporated after each addition. Add the sugar and cornstarch and mix until ingredients are combined, about 1 minute.
Divide the cream cheese filling between the two cake pans spreading filling with the back of a spoon evenly over cake batter. Sprinkle the raspberries and huckleberries over the cream cheese filling.
For crumb topping: Combine the flour and sugar in a bowl. Cut the butter into 1/4 inch pieces and drop them into the bowl of dry ingredients. Using your fingers, work the butter into the flour until the mixture is coarse and crumbly. Sprinkle the crumb evenly over berries between the two pans.
Bake cakes until set, about 45 minutes to an hour. Let cakes cool completely before unmolding.