Preheat the oven to 350°F (175°C) and lightly grease a standard loaf pan with nonstick spray. For easy removal, you can also line the pan with a parchment paper sling.

In a large mixing bowl, combine the oil and 1 cup of granulated sugar. Finely zest all the lemons you’re using directly into the bowl and whisk the mixture together. Add the eggs, vanilla (if using), and yogurt, whisking until smooth and well blended.

Sprinkle the baking powder and salt evenly over the surface of the mixture, then whisk thoroughly to ensure everything is evenly distributed. Add the flour and blueberries, stirring gently just until combined—avoid overmixing.

Pour the batter into the prepared loaf pan and bake for 60 to 75 minutes, or until a toothpick inserted into the center comes out clean.

While the cake is baking, juice the zested lemons to yield about ⅓ cup of juice. Place the juice in a small saucepan with the remaining 1 tablespoon of sugar and heat over medium, stirring until the sugar is fully dissolved.

As soon as the cake comes out of the oven, brush the warm lemon syrup over the top. If the syrup isn’t soaking in easily, use a skewer to poke small holes across the surface of the cake to help it absorb.

Allow the cake to cool completely in the pan. Once fully cooled, run a knife around the edges to loosen it and carefully transfer it to a serving plate. Dust with powdered sugar if desired and slice into 1-inch pieces to serve.

Make ahead: The cake keeps well at room temperature for up to 3 days, or in the refrigerator for up to 1 week. It also freezes beautifully—wrap it tightly in plastic wrap, and let it defrost at room temperature a few hours before serving.