For the lemon streusel:
1. In a small bowl, combine sugar and salt. Add lemon zest and stir thoroughly to combine. A pestle works great here, but a spoon or fork is just fine. Stir together for a few minutes until the lemon zest releases its oils, becoming fragrant and moistening the sugar.
2. Add flour; stir to combine.
3. Add butter and cut into dry ingredients until everything is well blended and mixture resembles coarse crumbs.
For the wild huckleberry tea cake:
1. Preheat oven to 350° F. Butter a 9x5 inch loaf pan and line the bottom with parchment, or leave parchment hanging over the sides if you want easy "handles" to remove the cake from the pan after baking.
2. In a bowl or liquid measuring cup, mix together wet ingredients (egg yolks, buttermilk, and vanilla).
3. In a separate bowl, mix together dry ingredients (flours, baking powder, baking soda, and salt).
4. Cream butter and cream cheese together using a stand mixer fitted with the paddle attachment or electric beaters. Cream until super soft and smooth, 2-3 minutes. Add sugar and lemon zest; beat until combined.
5. Add about 1/3 of the dry mixture to butter mixture and blend until almost combined. Pour in about 1/2 of the wet mixture; stir until almost combined. Alternate the remaining dry and wet ingredients two more times, until all ingredients are incorporated together. Do not overmix!
6. Fold in huckleberries. Pour cake batter into prepared pan and use the back of a spoon or an offset spatula to smooth it out. Top with lemon streusel, distributing the streusel evenly over the cake batter.
7. Bake for about 55-65 minutes, or until toothpick inserted in center comes out clean and streusel is lightly browned. Allow to cool.
For the huckleberry glaze:
1. If berries are frozen, allow them to thaw before making the glaze.
2. Press berries into a fine-mesh sieve to extract juices, leaving behind the skins and any seeds.
3. Whisk powdered sugar into berry juice until completely smooth. Depending on your berries, you may need a little more or a little less powdered sugar to get the thickness just right. It should be pourable but thick. If it's too thin, it will seep into the cake and disappear!
When the cake is cool, remove it from the pan and drizzle with the glaze. Serve thick slices warm or room temperature. Great in the morning with a strong cup of coffee!