Preheat oven to 150C. Spread blanched almonds on an oven tray, toast until golden and fragrant (6-8 minutes). Cool, finely grind in a food processor, set aside.
Whisk eggwhites in an electric mixer until soft peaks form, gradually add sugar, whisking continuously to incorporate, until all sugar is added and meringue is smooth and glossy (3-5 minutes). Fold in lemon rind, toasted almonds and cornflour.
Increase oven to 180C. Shape mixture with a teaspoon into 3cm mounds, place on a baking tray lined with baking paper, add a natural almond in the centre of each and bake in batches until puffed and starting to crack (8-10 minutes), then cool on tray. Almendrados will keep, stored in an airtight container, for about a week.