Preheat your oven to 350 degrees Fahrenheit.
In a bowl, combine the flour, baking powder, baking soda, and salt, then set this mixture aside.
In another bowl, whisk together the sugar and melted butter until well combined.
Add the olive oil to the sugar and butter mixture.
Crack the eggs into the wet mixture and mix well.
Stir in the sourdough starter and milk until fully incorporated.
Add the lemon juice, lemon zest, and vanilla to the wet ingredients, mixing thoroughly.
Gradually combine the dry ingredients with the wet ingredients until just mixed.
Gently fold in the blueberries into the batter.
Grease your loaf pans and pour the batter evenly into them.
Bake in the preheated oven for about 40 minutes, or until the tops are golden and a toothpick inserted comes out clean.
While the cakes are baking, prepare the lemon glaze by mixing lemon juice with powdered sugar until you achieve your desired consistency.
Once the cakes are out of the oven, allow them to cool for about five minutes before glazing them while they are still warm.
