Preheat the oven to 325 degrees F. Grease a 9 inch spring form or cake pan with butter.
Prepare the streusel by combining the brown sugar, nuts and cinnamon in a bowl. Set aside.
Whisk the flour, baking powder and baking soda together in a bowl.
Using a stand mixer, beat the softened butter with the granulated sugar on med-high speed until light and fluffy.
Add the honey and beat for another 30 seconds. Add the vanilla and eggs one at a time scraping down after each addition.
Add the dried lavender and mix for 30 seconds on low speed.
Add half of the sour cream and half of the flour. Mix and then add the rest of the sour cream and flour. Mix well.
Spread half of the batter into the prepared pan and sprinkle half of the streusel on top.
Pour the rest of the batter into the pan and spread out evenly. Top with more of the streusel and place in the oven.
Check the cake after 30 minutes and using a toothpick, look for it to come out of the cake clean with no crumbs or wetness. It will probably take closer to 40-45 minutes though. If you gently push the top of the cake, it should spring back.
Let cool before slicing. Store covered at room temperature for up to 3 days.
If you don't like walnuts, feel free to switch to any other kind of nut.