Preheat the oven to 300°F/150°C. Grease a tube pan generously with baking spray and set aside.
Cream butter and sugar on high in a stand mixer or with a hand mixer until it's fluffy and starting to look white (5-7 minutes).
Add the eggs, one at a time, beating them between each addition.
Mix the flour, baking powder, salt, and lemon zest in a medium bowl.
Next, add the dry ingredients, alternating with the buttermilk. Start with ⅓ of the dry, then ½ of the buttermilk, mix for a while, then add another ⅓ of the dry ingredients, followed by the rest of the buttermilk, and mix. Then add the last ⅓ of the dry ingredients and mix until just combined.
Place the chocolate chips in a bowl and add the reserved tablespoon of flour. Mix to thoroughly coat the chocolate chips.
Add the vanilla extract and coated chocolate chips to the cake batter and fold gently, scraping down the sides in the bowl in between.
Pour the batter into a greased bundt pan and tap it on the work surface to eliminate large air bubbles.
Bake at 300℉ (150℃) until a toothpick inserted into the cake's center comes out clean (50-60 minutes).
Cool for 15-20 minutes, flip the cake over on a rack to release, and cool completely. While the cake is baking, proceed with the ganache glaze.