Wash lemon hot, dab dry. Squeeze the lemon. Bring squeezed lemon, sugar and 1⁄4 l water to the boil. Take the pot off the stove. Stir in lavender flowers and lemon juice. Let the syrup cool down.
Pour lavender syrup through a fine sieve, fill into clean bottles and seal them. Place in a cool place and use within 2-3 weeks. Mix the syrup to taste with mineral water or sparkling wine.