Step 1

Preheat the oven to 350 F. Brush an 8-inch round cake pan with olive oil and dust with flour, tapping out the excess. Line the bottom with a round of parchment.

Step 2

Whisk the olive oil, sugar, lemon zest, eggs and yolk in a large bowl until the mixture is light, about 1 minute. Whisk in the milk, limoncello and vanilla until smooth. Add the 1½ cups flour, baking powder and 1/4 teaspoon salt, and whisk until just smooth.

Step 3

Pour the batter into the prepared pan and bake until a tester inserted in the center comes out clean, 30 to 35 minutes.

Step 4

Cool in the pan on a rack for 15 minutes, then unmold and cool completely before serving.