Whisk 200g of all-purpose flour, ½ teaspoon of baking powder, and ¼ teaspoon of baking soda.
Rub 150g of granulated sugar with the zest of 2 lemons. Whisk in 50g of vegetable oil, 30g of melted unsalted butter, 1 teaspoon of vanilla extract, ½ teaspoon of salt, 45g of lemon juice, and 1 large egg.
Stir in the flour mixture until no dry patches remain. Cover and refrigerate for 2-3 hours, until firm.
Preheat the oven to 350°F / 175°C. Line baking sheets with parchment paper. Put 65g of granulated sugar and 75g of icing sugar in separate bowls.
Scoop 23g portions of dough. Roll each in granulated sugar, then generously in icing sugar. Space apart on the baking sheets.
Bake for 11-13 minutes, rotating the baking sheets halfway, until edges are firm and centers set. Let cool on the baking sheets.
