Preheat the oven to 350℉.
Fully melt the butter, then allow it to cool until just warm.
Grease your loaf pan thoroughly, or you can line it with parchment paper for easy removal.
In your large bowl, combine melted butter, sugar, eggs, sourdough discard, vanilla, lemon juice, lemon zest, and lemon oil.
In another smaller bowl, mix flour, salt, baking powder, and baking soda.
Slowly incorporate the dry ingredients into the wet ingredients without over-mixing.
Scrape the batter into the prepared loaf pan.
Bake in the preheated oven for 55-65 minutes until a toothpick inserted in the center comes out clean and the loaf is golden brown.
Cool for at least 20 minutes before adding the glaze.
While the loaf cools, whisk together the glaze ingredients until smooth.
Pour the glaze evenly over the top, slice, and enjoy.