Heat oven to 350° F. Grease a 6-cup bundt pan well with butter, making sure to get every nook and cranny. If you’d like to use a 12-cup pan, just double the recipe. Alternately, you can use cooking spray (try to find a natural, propellent free oil-spray or make your own!) If using the latter, use right before filling the tin so the spray doesn’t pool at the bottom of your pan.

Weight the flour out into a small bowl. Add baking powder and salt. Sift the flour mixture into a medium bowl, dumping any salt that doesn’t make it through the sieve in at the end. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment cream the solid brown butter, olive oil, and the brown & white sugar until very light and fluffy, about 6 minutes, making sure to scrape the bowl down half way through.

When you’re finished creaming the butter and sugar, scrape the bowl yet again, and, with the mixer on low add the eggs one at a time, incorporated the first before adding the second. After the second egg is incorporated add the vanilla. Don’t forget the vanilla! I always forget the vanilla.

With the mixer still on low, add 1/3 of the flour mixture followed by half of the buttermilk, alternating with the next 1/3 of the flour mixture, then the rest of the buttermilk. Turn the mixer off and, using a rubber spatula (the one you’ve been scraping down your bowl with…because you have been scraping down your bowl, right?), mix in the last 1/3 of the flour mixture along with the rosemary by hand to prevent over mixing. Be sure to scrape the bottom! Gently fold in the blueberries.

Spoon the batter into the prepared tin, smooth the top, bang it against the counter 3-4 times to get rid of air bubbles, and bake at 350° F for 30-45 minutes (if doubling the recipe for a 12-cup bundt pan or if using a 6-cup bundt pan with no hole as I have here, increase cooking time to 1 hour – 1 hour 15 minutes and cover with foil after 45 minutes) or until golden brown and a toothpick inserted comes out clean. Again, if at any point the top is a deep, golden brown, but then center is still not cooked, cover the top with tin foil and continue to bake until a toothpick comes out clean.

Cool in pan 20 minutes. Run a thin knife around the edge of the cake, and then invert onto a cooling rack to finish cooling. Meanwhile, make your glaze. Sift the powdered sugar into a bowl and then whisk in the buttermilk. Set aside, whisking every so often to prevent drying out while the cake finishes cooling. Once the cake has reached room temperature, spoon the glaze over the top, allowing it to drip down the sides. Let glaze dry. Slice and enjoy with a cup of coffee!