Make the brown butter first! In a small saucepan on medium heat, place the butter in the pan. Keep an eye on it and let it melt almost entirely. Begin to whisk it as it bubbles. It may foam. Keep whisking and when you see brown bits starting to form, turn off the heat and continue whisking for 20 seconds. Transfer the butter to a small bowl, making sure to get all the brown bits from the bottom of the pan. Set aside to cool completely.
In a large bowl, combine the sugar and lemon zest by massaging the zest into the sugar with your fingertips. Do this until the mixture resembles wet sand. Set aside.
When the butter is cooled completely, continue on! Oil a 10-inch Bundt pan (if you know yours sticks or you aren’t sure, then carefully butter and flour it). Preheat the oven to 350F.
To the sugar mixture, add the 4 eggs and the sourdough starter then whisk until fluffy. Add the yogurt, lemon juice, and vanilla and whisk until combined.
Sift the flour, baking soda, baking powder, and salt over the batter mixture. Fold the batter with a spatula a few times, then pour in the brown butter. Continue to fold until no streaks remain.
Pour the batter evenly into the pan. Even out the top with a spatula if necessary. Tap the pan once or twice on the counter, then place in the oven to bake for 50 minutes. Let cool for 10 minutes then flip the cake onto a wire rack.
While the cake cools, make the glaze. Whisk the glaze ingredients together until smooth. When the cake is fully cooled, place it on the serving dish and drizzle the glaze on top. Enjoy! Let me know what you think below in the comments or on Instagram @higheralchemybaking!