Preheat the oven to 350F degrees, rack in the middle. Butter a 1-pound loaf pan, and line with parchment paper. Alternately, you could just butter and flour the pan,.
In a medium bowl, whisk together the flour, oats, baking powder, baking soda, salt, thyme, and rosemary. Set aside.
In a separate large bowl beat the butter with an electric mixer or by hand - until light and fluffy.
Drizzle in the maple syrup and beat until well incorporated, scrape down the sides of the bowl a couple times along the way.
Beat in the egg, lemon zest, and vanilla extract, scraping the sides again. Add half of the flour, stir just a bit, now add a splash of the buttermilk, stir again, but not too much.
Add the rest of the flour and stir a bit, and now the rest of the buttermilk. Stir until everything barely comes together and then very gently fold in one cup of the huckleberries. Scrape the batter evenly into the prepared pan and set aside.
To make the streusel topping, place the flour, butter, maple sugar, thyme and pecans in a food processor and pulse 20-30 times or until the topping is a bit beyond sandy/crumbly. It should be moist-looking - on its way to being slightly doughy.
Crumble 2/3 of it over the cake batter, sprinkle the remaining 1/3 cup huckleberries on top of that, and then add the last of the crumble. Barely pat in place with your fingertips.
Place the coffee cake in the oven and bake for 45-50 minutes or until the top is golden and a toothpick inserted into the center of the cake comes out clean.
Let the cake cool for five minutes and then remove it from the pan to cool on a rack (this way the cake won't steam in the pan as it's cooling.