Soak gelatine in cold water. Line the bottom of an ovenproof dish (approx. 17 x 17 cm) with the lady fingers. Mix lemonade and 3 tablespoons of lemon liqueur and sprinkle the sponge fingers with it. Stir the sour cream, sugar and yoghurt with the whisk of the hand mixer for about 5 minutes until creamy. Squeeze out the gelatine, dissolve it and mix with approx. 3 tablespoons of the yoghurt cream.
Stir the gelatine into the rest of the yoghurt cream. Wash the limes and lemon and rub dry. Thinly grate the zest of 1 lime and the lemon. Stir the zest and 3 tablespoons of lemon liqueur into the cream. Whip cream until stiff and fold in. Pour the cream into the mould and chill for at least 3 hours. Remove the zest of the other lime using a zest ripper. Peel lime and lemon so that the white skin is completely removed. Remove the fillets between the parting skins.
Whip cream until stiff and fold in. Pour the cream into the mould and chill for at least 3 hours. Remove the zest of the other lime using a zest ripper. Peel lime and lemon so that the white skin is completely removed. Remove the fillets between the parting skins. Decorate the tiramisu with the fillets, lime zests and yellow sugar
waiting time approx. 2 hours