Preheat your oven to 180°C/356 °F (160°C/350°F fan). Butter a 20 x 6 cm (8" x 2.36") round pan and line the bottom with parchment paper. See note (1) for using a loaf pan.

In a medium bowl, sift together the flour, baking powder, and salt. Set aside.

In a small bowl, rub the lemon zest into the granulated sugar using a fork or your fingertips until fragrant.

In a large mixing bowl (or stand mixer fitted with the paddle attachment), beat the softened butter on medium speed until creamy (about 1 minute). Add the lemon-infused sugar and beat until light and fluffy, about 4–5 minutes. Stir in the vegetable oil until well incorporated.

Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl.

Stir in the lemon juice and the optional rum or vanilla. (Do not worry it the batter curdles at this point, it will smooth out when you add the flour.)

Fold in the sifted flour mixture by hand (or mix on the lowest speed) just until the flour disappears.

💡 Do not overmix at this stage, or the cake may become tough.

Pour the batter into the prepared pan. Bake for 45 to 55 minutes, or until a toothpick inserted into the center comes out clean. Remove from the oven and let the cake cool in the pan for 10 minutes, then gently run a knife around the edge and invert it onto a wire rack.

Cover with glaze while the cake is still warm. Allow to cool completely before slicing.