Wash the limes in hot water and dry them. Peel in thin strips with a zest ripper and then chop finely. Squeeze the limes. Grease a springform pan (26 cm Ø). Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer).
Separate the eggs for the dough. Beat the egg whites until stiff, while pouring in 50 g sugar. Cream 125 g butter and 250 g sugar with the whisks of the mixer. Add lime juice, except 1 tablespoon, and lime zest, except 1 tablespoon, and continue stirring for about 3 minutes.
Stir the egg yolks one after the other into the sugar mixture. Stir in almonds. Fold in ricotta and grated coconut. Add the beaten egg white to the dough in 2 portions and fold in.
Fill the dough into the springform pan and smooth it down. Bake in a hot oven for about 50 minutes. Take out, let it cool down briefly in the tin, then remove from the tin and let it cool down.
For the Frosting, whisk 125 g butter with the whisks of the mixer until light creamy and stir in icing sugar. Add 1 pinch of salt, remaining lime zest and lime juice, continue stirring for about 3 minutes. Spread the cake all around with the frosting, sprinkle with coconut chips and decorate with lime wedges as desired.