Heat the oven to 175 C / 350 F. Grease a 9x5 inch loaf pan with a little olive oil and line it with a strip of parchment paper, leaving an overhang on the long sides.

Add the sugar and lemon zest to a large mixing bowl. Rub them together with your fingertips for about 30 seconds until the sugar looks damp and smells strongly of lemon.

Add the eggs, olive oil, oat milk, lemon juice, and vanilla extract to the bowl. Whisk until the mixture is pale and uniform, about 1 minute.

Add the flour, baking powder, and salt. Fold with a flexible spatula until no dry streaks remain. Stop mixing as soon as the batter is smooth.

Pour the batter into the prepared pan and smooth the top with the spatula. Tap the pan gently on the counter once to release any air pockets.

Bake for 45 to 55 minutes, until the top is golden and a wooden skewer inserted into the center comes out with just a few moist crumbs. If the top browns too fast after 35 minutes, lay a loose piece of foil over it.

Let the loaf cool in the pan for 10 minutes, then lift it out using the parchment overhang and transfer to a wire rack. Cool for at least 20 minutes before slicing.